Yeah besides aesthetic preferences change over time and people just grow to prefer what’s ever modern. Or to tolerate it and then that becomes the standard. I don’t remember people bitching that phones were too thick back in the day. Obviously their primary motivation is planned obsolescence and increased phone sales.

It’s incredibly naive to assume there’s any other reason. I’m just absolutely no reason for them to stick glue on the battery or the serialize parts, other than to sell more phones and warranty plans.