I prefer that feature massively. Being on hold sucks, you can't fully commit to doing another task because you need to listen out for the fuzzy elevator music to switch to a human voice. Even worse when the fuzzy music switches to a recorded human voice every 30 seconds to remind you you're still on hold.
Having a call back means I can forget about it and go on with my day until they call me.
...I wonder if there's a meaningful way to prevent companies from saying they're going to do this, and then just "losing" 80% of the callbacks they're supposed to give. Or giving them at 1AM (hey, it's 10:30AM in Mumbai where the off-hours call center is!).
Waiting for a callback is unquestionably way better than waiting on hold, but I would still need to make sure I'm in a position to be taking that call and actually handling whatever it requires at any given time during the waiting period, so things like going shopping or being in a place with poor cell signal (like my office!) aren't good options—and what happens if I'm not available the moment they call? Can they just say "oh, well, couldn't reach customer" and force me to start the process again?
Having a call back means I can forget about it and go on with my day until they call me.