That’s the point, it is so you don’t have to require any special tools that you have to purchase or rent, or having to deal with glue and all that crap.

But Why? If I switch the battery in my phone once after like 2-3 years, I can deal with that once just fine.

You think because it’s replaceable it can’t be compact and waterproof? Ever used a watch?

Ye, both watches and airtags have fairly small and round openings to seal up. Also airtags are only ip67, phones are ip68 which is a lot more difficult to achieve.

With a phone, you will then need to separate the battery from the rest of the phone, with some form of "compartment", that will use quite a lot of internal space and therefore make the packaging a lot worse, resulting in a smaller battery. You will then need some form of lid on the back that can be opened / closed again, and is still waterproof to ip68 or more. That requires a lot of pressure on quite complicated seals, with a copmlicated mechanism to hold the lid closed all around the edge. All of this will at least triple the cost of the phone case, which is already a very expensive point on the bom.

People complain phones are too expensive, but then they ask for uneccesary stuff like this...

That's the point, it is so you don't have to require any special tools that you have to purchase or rent, or having to deal with glue and all that crap.

That's not the point. The point is reduce electronic waste and improve lithium recovery. The regulations have the following provisions for replaceable batteries

A portable battery should be considered to be removable by the end-user when it can be removed with the use of commercially available tools and without requiring the use of specialised tools, unless they are provided free of charge, or proprietary tools, thermal energy or solvents to disassemble it.

Addition provision for waterproofing also may apply

To ensure the safety of end-users, this Regulation should provide for a limited derogation for portable batteries from the removability and replaceability requirements set for portable batteries concerning appliances that incorporate portable batteries and that are specifically designed to be used, for the majority of the active service of the appliance, in an environment that is regularly subject to splashing water, water streams or water immersion and that are intended to be washable or rinseable. ... Where the derogation applies, the product should be designed in such a way as to make the battery removable and replaceable only by independent professionals, and not by end-users.

So basically most companies will opt either provide the tools for free like some already do or just claim that watches and headphones undergo enough contact with sweat and oils that apply for the derogation