With some effort I can understand the demand for one of them, but why there are so many of them and why even more are going to be issued? Does this mean that previously issued "stable" coins need improvement? Or, maybe, it means that older coins have compromised their reputation already and people expect that new ones will be more trusted?
Probably because issuers are making money out of them? Having their own must strengthen their ecosystem or something because they won't have to rely on someone else's.
Newer ones like Circle's USDC are apparently more trustworthy because they're issued by a regulated entity, but I'd have to read up more about them. USDC specifically is also trading above the dollar right now which might mean that people are dropping USDT for them.