The main reason: Batteries. Build in Lithium batteries die permanently after three years, give or take, and are difficult to replace giving your device a limited lifespan by design (I hate that!), and NiMH ones require frequent recharging, for example, I'm lucky to get 8-10 hours from the NiMH's in my Ourobouros mouse (not so bad if your mouse has a charging dock, which the Ourobouros does, but not many do, which is stupid for how much some of them cost). And Alkaline batteries... heh... don't make me laugh, oh gods of Total Cost of Ownership.
For things that move a lot, like, I dunno, mice, wireless is handy, and some actually come with charging docks and user replaceable batteries. Yay. Tangled mouse cables have caused me to wipe our MMORPG raids numerous times. That's embarrassing and I changed to wireless mice for gaming (to be clear, I only use mice for gaming). But for everything else, it's about the batteries. Why is a cable leading to your keyboard, trackball, flightstick, or Wacom tablet, which doesn't move during normal operations, a bad thing? And why should I have to keep track the battery remaining life percentile or charge cycles on something that shouldn't even need batteries?
I have a similar rant about smart-watches. Not until they last a week. I want at least one portable device in my life that I don't have to feed electricity to every single night, thank you very much.
As for networking.... well... Gigabit Ethernet might be almost 20 years old, but it's still waaaaay faster than the practical implementations of any consumer wireless networking. And if you live in apartments, way less glitchy.
Now, if they made a desk surface that was itself a large inductive charger (and safe to use for extended periods of time- I'm waiting to hear this from a non-industry-sponsored peer reviewed article, thank you very much) , and inductive charging was actually common on devices, now we'd be talking.