I've used it on a motorcycle attachment for a long trip before. The same pop socket was then attached to a new phone and used for another 2 years. Maybe I lucked out with that model or it just sticks to flat cases better.

Experience or feeling? I've had three or four over the last 10 years, the plastic starts disintegrating from constant use after a couple years, while the adhesive still sticks (and all that while being repositionable and reusable, I've swapped cases but kept the pop socket), so can't relate tbh

They are applied with an adhesive strip, not suction cup.

Unless you are very unlucky when you accidentally Thwap! one on your forehead. Uncle Stu had a perfectly round hickey on his forehead for like two weeks.