The closest I can get to an explanation is that someone at Apple lives in perpetual A E S T H E T I C terror of someone somewhere leaving their mouse plugged in all the time
honestly it's not THAT bad a decision. you need to plug the mouse in for like only a minute to get a month of battery life. you aren't going to be in a situation where you need to use the mouse when it's charging.
When the battery dies it just becomes e-waste — if you could charge and use it at the same time, then it could at least still be useful as a wired mouse for many more years.
If it has pass thru charging, yes. Otherwise, it’s just ewaste.
Unless the mouse body is sealed like ultrasound welds, it’s openable and the battery is a replaceable commodity. Thirty seconds on temu, then 15 min w a soldering iron and mouse is back in business.
Unless they serialized the mouse. Then you’re looking at pulling the battery, pulling whatever chip identifies it, and sweating it on to the new one. I want to say there’s no way they’d serialize a mouse battery but it is apple after all so who even knows.