why do my daily opponents keep closing their accounts?

Yeah, I have noticed this phenomenon too. It is kind of strange. The only reason I can come up with is frustration or some people just quit chess. But in that case you don't need to really close your account. You can just your account exist and not play anymore. At least for a while.
But there might be also some nefarious reasons. Like sandbagging. There is an option for reporting sandbagging, but I'm not sure when to make such a report and I don't know if it is helpful to report a closed account. But it does look strange and sus imo. But maybe there is something we don't know.

People, I'm not saying who, but people in general might do things they regret when tilted, now I am not talking about anyone in particular, and certainly not from experience.
But people might do things they regret when tilted.