[ceejayoz]

It's not hard, but it takes up more space than a permanently affixed battery (which doesn't need a user-facing battery bay, can be permanently wired in, etc.) and introduces moving parts (I recall having my battery cover open and the battery skitter across the floor whenever I'd drop my old flip phone).

Apple has been moving in the same direction for laptops. http://ifixit.org/blog/2763/the-new-macbook-pro-unfixable-un...

https://d3nevzfk7ii3be.cloudfront.net/igi/PTdAj6LheOiy2Vu1.m... shows 8 of the 16 RAM chips (the others are on the other side) in a Macbook Air. Having them soldered straight on the board means you can't replace 'em, but it also means they use a lot less space than a stick of RAM.