The market has spoken. If there were enough normies who would want bulky phones with removable batteries they would buy them. But they don’t… They want shinny unibody phones with locked bootloaders and proprietary connectors. Only a small minority cares about these issues.
Why would they incur the cost of retrofitting their factories or production process for a small minority that wants removable batteries. If there was enough demand they’d know because they’d market it as a feature and profit from it. Truth is normies don’t care or prefer the look/feel of soldered batteries and unibody slim phones. I’d personally like all phones to have an unlocked bootloader but I know that’s not what the market wants and manufacturers rarely offer it. I can’t force them to make one for me so I just ignore them and buy the one with an unlocked bootloader.