I once had a conversation with a man of the WWII generation. I asked him what was the biggest difference between now (circa 1990) and when he grew up. I thought he was going to expound on morals and manners. Instead he said the biggest difference was all the trash, the stuff you throw away now. In the old days, you threw nothing away.
Is planned obsolescence built in? Not necessarily. I think most decisions are based on lowest cost and user demand. If having a replaceable battery were as big a selling point as big high res screen or sleek thin light weight body, we would have replaceable battery. There is no need to plan for something when the path of least resistance leads to the same destination anyway.
Btw even the one plus one phone does not have a removable battery. They explain why here
https://forums.oneplus.net/threads/t...-reliable.327/