The problem is that guys on the 60-day IL revert to the active 40-man roster following the season, so Barker would have been clogging a spot there all offseason before they could place him back on the 60-day IL next spring. All the while he'd be drawing a major league salary and service time, while it is likely he won't even be able to competitively pitch again until 2024, when he'd be a 32-year-old rookie. Just really disastrous timing for this injury, as he'd been pitching well and looked to be a guy who was going to be yo-yoing back and forth between AAA and the MLB roster this year.
Teams will stand with guys through this sort of rehab process if they feel there is enough upside to be had. But Barker is a guy who maxes out in the low 90s with his FB, and while he has been extremely effective in the upper minors, his upside is as a low-end middle relief arm at the MLB level at best. It's a tough, sometimes pretty crappy business, especially for the guys on the fringe.