People who enjoy latency free and battery free mice. If its at a desktop there is really no reason to not use a wired mouse. And a wired keyboard is basically essential since bluetooth doesn't work before the OS has booted.
While you're correct, there's lots of plain-RF wireless mice and keyboards that work just fine before the OS loads, and many people confuse "bluetooth" with "all wireless".
Plus, some wireless mice are actually faster than some wired mice.
There's one reason: one less wire to deal with. I bought a Logitech G703 just to avoid the clutter and tugging on the cable when using it (and not having to buy or build a dampener for the cable). It has a cable I can use to charge it or use when it's low on charge, and I can't notice any difference in latency when it's wired or wireless, or compared to any wired mouse I've ever used. I'm also not playing many FPS, and definitely not anywhere near a competitive level, so even if there is some measurable latency it simply makes no difference to me.
The wireless dongle is plugged into a USB port on my monitor so it's only about a foot away, though not quite direct LOS. And if I wanted to fork over $100 for Logitech's wireless charging mousepad, I'd never have to plug it in again. I probably won't, but it's an option.
TL;DR: wireless and wired gaming mice have the same response times, but normal wireless office mice have slower response times than their gaming counterparts.
My biggest issue with wireless office mice is that if the laptop de-prioritises bluetooth interrupts due to CPU load or whatever, then you get this really laggy response. I'm not entirely sure exactly what's going on, but if I open something heavy on my work laptop the mouse will have a 0.5-1 second delay in responding.
This doesn't affect the touchpad, which I presume is running over a different protocol that has more real-time interrupts.
