There's more to these than just batteries. If they had sealed-in a rechargeable battery then you'd have to throw out the whole thing and buy a new one once it stopped holding a charge. This way you can just buy your own rechargeable CR2032 batteries.
I thought you were joking about rechargeable 2032's... and I was wrong. Had no idea. I don't know why I didn't look into these before; I have a number of things that use 2032's that I can use this for.
I looked in to it and it looked like they were at a different voltage which could be an issue. Also devices that use these go flat so rarely that it will take decades to pay off the charger. But I guess if you have 20 airtags that could come faster.
Be careful with that one, many rechargeables aren't suitable for low current/long lasting applications due to self-discharge. There are "low self-discharge" cells, but not sure about that in a CR2032 form factor.
Better to replace a single battery after a year than throw away an entire perfectly good speaker and earbud and a spent battery after two years, like with airpods.
Many of the competitors are entirely disposable. I’m not aware of any very small ones that are rechargeable.