Because they don't want to. Also e.g. the Pixel 6 has an element in the display assembly that makes the repair easier + a glue that melts well. Older iPhones

Because they don't want to. Also e.g. the Pixel 6 has an element in the display assembly that makes the repair easier + a glue that melts well. Older iPhones were also easier to open, but their glue gets seems to get more aggressive each year. The whole access via glued display construction can be fairly easy to work with when the display assembly is done right and they use a glue that melts well. And sure, the even easier access design around screws is harder to do, but also possible. See the iPhone 6, which used screws and a much weaker glue.