Most modern low end boards don't have this. And a very big chunk of desktop computers in use nowadays probably fall in the having a low end board category or being old enough for that to not be a feature. (my desktop is in the first category lol)
Fair, although given M.2 is just PCI-E, a quick search on aliexpress shows adapters for under a fiver, might be the best route to a known good option (assuming those adapters aren't problematic themselves, but they should be simple, also assuming most people have a free PCI-E slot these days, outside of ITX boards, but those not having an M.2 for wifi seem unlikely).