Earlier quoted context omitted.
> Where does this crazy idea come from that you have to glue shut a device to make it waterproof? Glue helps with heat dissipation, physical shocks, vibration knocking plugs loose, provides electrical insulation, chemical resistance, and makes the components less able to vibrate over time and knock things loose, makes sensor positioning more stable, and even makes things easier to assemble since less individual faste…
Your response doesn't actually address the point you quoted. But yeah. You can either do thoughtful engineering and careful assembly... or you can achieve close to the same thing with glue.
Setting a part in a jig, brushing a dab of glue, and setting a second part on top is much faster than the same process but fastening a couple screws to the appropriate tightness. It's also less error prone and creates a better bond between the parts.
Apple and Samsung pump out tens of millions of phones a quarter. The more effort required for each stage of assembly ends up the difference of millions of phones manufactured in the same period of time.