In technical terms any computer can be a server. Just look at the BBSs that was run out of C64s and similar back in the day.

But a server that can't be reliably reached is a useless server.

And the BBSs worked back in the day because dialing the same number days, weeks, even months inbetween would lead you to the same BBS if the computer was still running.

A domestic internet connection is simply not reliable enough for that. Yes, if nothing happens electrically at either the customer or ISP end the IP will remain for some time. But have a power failure and it is likely that the IP will be reassigned. And that random aspect, that sometimes you can retain the address for months, and other times get it changed within hours, do not help.