This isn't a surprise. A few reasons why:
1. Refsnyder has only one more minor league option. Even if Refsnyder remains with the Yankees organization, it's hard to imagine his final option not being burned this year. In order to retain it, he'd have to be on the 25-man roster all season. Barring a slew of injuries, that's not happening. That means in 2018, if still with the Yankees, he would be subject to waivers if the front office decided he wasn't worthy of the 25-man roster. Thus, the Yankees might as well try to get something for him before waivers becomes the last resort.
Of course, the Yankees don't have to deal him now. They could wait until midseason, the offseason, or next spring. The soon to be 26 year old's remaining option allows them that flexibility. However, waiting until the offseason or next spring will deplete his value. Admittedly, his value isn't much to begin with, but the current ability to shuttle him between the majors and Triple-A could make him a tad more attractive for another club. Without any options remaining in the offseason or next March, Refsnyder's trade value would be minimized.
2. His lack of position. The Yankees hoped that the former 5th rounder could grow into a utility role, trying him at various positions around the diamond and in the outfield. Whether it was first base, second base, third base, or the outfield, the Yankees have tried almost everything without much luck. Scouts evaluations of Refsnyder's glove work have been shoddy, and it's evident that the Yankees aren't big fans of his fielding given the unwillingness to play him at second or third base anymore (he's exclusively played the outfield and first base this spring).
Refsnyder seems most tolerable in left or right field. However, the problem with leaving him the outfield corner permanently is his bat. Refsnyder is a contact oriented hitter with little power, which doesn't fit the mold of the desirable power hitting corner outfielder. One doesn't have to have power to play second base, but when it comes to the outfield, it's hard to get by without power in right or left field unless there's another supreme skill compensating for it (see: Brett Gardner's defense). Maybe another team in need of a second baseman would be willing to give Refsnyder a final opportunity at second, but it won't be the Yankees.
3. He's been surpassed on the depth chart, and is at risk of falling down further. If something happened to Starlin Castro at second, who would step in? Not Refsnyder. The Yankees clearly have given up on him as a second baseman; he hasn't played the position all spring. That means that Ronald Torreyes comes before Refsnyder. Even non-roster guys like Ruben Tejada or Donovan Solano might get an opportunity before Refsnyder at the keystone.
Before Chris Carter was added, it appeared that Refsnyder might have had a chance to beat out Tyler Austin for a platoon with Greg Bird at first base. That's out of the question now, and even if Austin was healthy, it's unlikely that Refsnyder was favored in that competition.
Third base? Not an option. He hasn't seen game action at the position this spring. Ronald Torreyes or a non-roster invitee would come before Refsnyder.
In the outfield, he's looking up to Aaron Judge and Aaron Hicks in the corner outfield. Austin has him beat there, too. Don't forget Mason Williams, who if healthy, is preferable to Refsnyder.
Then there are the prospects. Tyler Wade is being groomed for a utility role, a job that Refsnyder hasn't been able to grab because of his defensive issues. If he isn't already, Wade will be a better option than Refsnyder soon. If you want to think of Refsnyder purely as an outfielder, he's out of luck there too. Whether it's Clint Frazier and Dustin Fowler ascending the ranks, or Mason Williams still hanging around, Refsnyder is soon to be an inferior option (if not already). There are 40-man roster implications with these players of course, but on sheer ability and long-term plans, Refsnyder isn't an option.
All told, plummeting on the depth chart is another way of saying that the Yankees don't view him as a part of future Yankees teams. He may have figured out Triple-A pitching, but that can only take him so far in an organization as lush with young talent as the Yankees. Some other team might have interest in figuring out if his bat is worthy of major league play despite his defensive shortcomings.
4. 40-man roster cram. There are a handful of good prospects the Yankees will need to protect from the Rule 5 draft this offseason. The aforementioned Wade, Frazier, and Fowler are no doubters, along with others like Gleyber Torres. That's not a wholly inclusive list of guys who need protection, either. The Yankees need to make space on the roster for these prospects, so the writing is on the wall for someone like Refsnyder. He's not going to block anyone.
The Yankees can bide their time with Refsnyder because the 40-man decisions aren't imminent, but they are certainly worth consideration. Timing is (almost) everything, though. Refsnyder's trade value will be down if they wait to deal him until they absolutely need to use his roster hold, so moving him now might be ideal.
Perhaps a trade doesn't come to fruition before Opening Day, but it would surprise me to see Refsnyder in the organization at season's end. Maybe he's kept around in Triple-A for a few months in order to provide injury depth (particularly with Tyler Austin out), but that's about as much as I can fathom. He's certainly not going to get many big league chances unless there's an array of health flare ups.
What will the Yankees get for Refsnyder? Very little. An iffy low level minor leaguer seems plausible. Maybe some cash or the vaunted player to be named later. Maximizing the return is important, but there's only so much that can be attained for a player who's stalled at the major league level with a dubious future.