I've worked in consumer electronics, batteries are built in because reviewers will endlessly trash a product that is just 1mm thicker than anything apple puts out, and they fawn over apple because the products are so thin.
If anyone releases a product that is just a tiny bit thicker than last year, except headlines like "new super-thick phone doesn't fit in pockets, causes back problems".
A small exaggeration? Not by far, reviewers nasty about device thickness.
Then 70% of people shove a case on and it really doesn't matter.
There are good water ingress reasons for non-replaceable batteries, making a device water proof and have a replaceable battery does add a good deal of thickness.
Anyway, you can get a battery replaced at a phone shop for a reasonable rate anyway, so IMHO it isn't as big of a deal now days.
No one wants to, but that is how many consumers decide on what to buy. It is especially how early adopters tuned into the review scene for their favorite products decide what to buy.
If anyone releases a product that is just a tiny bit thicker than last year, except headlines like "new super-thick phone doesn't fit in pockets, causes back problems".
A small exaggeration? Not by far, reviewers nasty about device thickness.
Then 70% of people shove a case on and it really doesn't matter.
There are good water ingress reasons for non-replaceable batteries, making a device water proof and have a replaceable battery does add a good deal of thickness.
Anyway, you can get a battery replaced at a phone shop for a reasonable rate anyway, so IMHO it isn't as big of a deal now days.