I wonder what the tradeoff will be? Smaller capacity batteries? Lower quality so the manufacturer can sell more replacements?
If you listen to the manufacturers, the result will be dogs and cats living together, mass hysteria!
Except that the replacement batteries are shit and the brand batteries are just expensive re-branded shit.
That is my experience. I have three phones with removable batteries, a Samsung from 2020 and two Alcatels which are newer, and in no case does the manufacturer sell batteries so I have to rely on questionable third parties.
Of course manufacturers use the excuse that people will buy questionable third-party batteries causing fires and whatnot, while not supplying the correct batteries themselves.
I replaced the batteries in old iPhones with $20 kits that included both the battery and the tool. It takes me an hour. They last just fine.
My batteries can be replaced by using a fingernail inserted into the notch in the rear cover to remove it.
I don't understand. Why *wouldn't* you want a battery operated tool, all else being equal? My drill, impact driver and jigsaw are all battery powered. I'm usually just doing short jobs, so it's enough to keep the second battery on the charger if I expect the first to run out. And the impact driver has more than enough torque. That way I don't need to worry about where I'm plugging it in, tripping over the cord, or keeping the cord out of the way of anything.
My corded power tools are more powerful, run continuously, and do not require a costly battery and charger. I have many cordless power tools, but I only rely on them for light duty tasks.
Honestly, I don't know what the issue is anyway. I typically keep a phone for two or three years [...]
That's the issue right there. 
Discarding a phone after only two or three years is wasteful. Why do you replace it after such a short time? I have not observed rapid technical progress over the past decade which would justify that. Weakening battery performance or lack of software upgrades seem the likely candidates -- and both are entirely due to the manufacturers' unwillingness to support their products through a decent lifecycle.
Unfortunately even if the battery is replaceable, there may be good reason to discard the phone.
I have changed the battery in my *unlocked* Samsung Galaxy XCover Pro, however fucking AT&T blocks firmware updates to their unlocked phones. By law they must unlock their phones so that they may be used with other carriers, but nothing requires that they do not cripple them.
So great, phones will be required to have user replaceable batteries, and the manufacturers and carriers will find some alternative way to enforce planned obsolescence.