Just something I was frustrated by ever since it became increasingly common even outside of smartphones and tablets.

For a few years now I increasingly see basically any battery powered product having mostly internal accumulator options(aka proprietary battery of uncertain ability to replace), especially in more expensive items in the category. Why?

I mean do see several advantages from the business side, I simply have no idea what advantage would there be for the actual user.

I could see it if the batteries had comparable lifespan to the product, which they most definitely do not unless the item is of truly bad quality.