I used to have a Galaxy S5, the model that usually comes up in these discussions. Now, I never went and threw it in a swimming pool, or pressure washed it, or whatever other ridiculous test you may come up with. But I did attach it to my motorbike's handlebars and rode around under heavy rain on more occasions than I care to remember.

It was often drenched to the point that the map on the screen was basically illegible without stopping and wiping off the water. But it never skipped a beat. Basically, I was the limiting factor and would eventually give up and find some hotel with a hot shower to pass the night.

They have, and people preferred smaller phones.

Why waste space for gaskets and o-rings when you can already get the battery changed out while you wait with glue? Glue is clearly the superior method, which is why almost the entire market has adopted it.

Heat pads exist even in the most basic repair shops. It's not advanced technology, no need to over-engineer it.