I know that I mentioned this in another thread, but most days I have at least one SackyG dollar in my pocket, and sometimes a SusanB. The change machine in the breakroom at my office gives them out, and all the vending machines there take them. I think they’re pretty handy.
Since they’re in my pocket as a result, I do end up spending them at retail stores from time to time, and pretty much no one blinks at them. However, I have never received one as change from a human. I think that the stores just don’t stock up on them - they don’t bother getting both $1 bills and $1 coins to give change with, they just pick the bills, so they don’t go into circulation from the stores. Obviously, they’re not going to go into circulation from ATM’s either (most of the ones I see are $20s only, with a few being $20/$10s, or an occasional $20/$5).
So, if I have a $1 in my pocket, it came from the change machine at work (coin) or as change from a retail transaction (usually a bill). I think the main reason there aren’t more in circulation is that retail places haven’t switched over to that being their main choice for $1s.