Here's the thing. There are still plenty of devices that only have 2.4Ghz radios. There's some cheaper stuff still made today with just 2.4Ghz. So you'd just cut out a load of devices from working straight out. This kind of thing needs to be done slowly. 3G was very different because phone makers generally always want the more modern technology and phones that didn't have radios capable of 4g or better really are just rare now.

But, there's also just no reason to. Have 2.4Ghz available doesn't hurt you, if you're not using it. Any chipset with 5Ghz is not costing more to also support 2.4. They're just all pretty much single chip solutions these days and the aerial is usually just a coil on the board somewhere. If your device works on 5Ghz it will use 5Ghz.

I'd also argue in real terms 5Ghz isn't much better than 2.4Ghz in terms of channel space in places that need to respect DFS rules you generally only get one 80Mhz channel that will definitely work, and if you're using 802.11ax 80Mhz is really the minimum you want to get even remotely close to the advertised rate. Everything else useful is either DFS or limited power (at least here in the UK, and I don't recall seeing the limited power channel as an option). Now, I've generally setup two wifi APs in my house, one on the only non DFS channel, and the other on a DFS channel. That way if the DFS channel gets knocked out there's a fallback to the already congested "main" 5Ghz channel.

I think the main point is, why remove something that doesn't really affect you but may well affect others?