It's not about being "more careful with it". You shouldn't have to think twice about sitting down with your iPhone in your SIDE POCKET. You shouldn't have to take it out of your pocket if you want to get in your car. Also, you could be extremely careful with it and still accidentally sit down or climb into a car with it in your pocket because we're conditioned to not have to worry about our phones being so weak that they'll break while doing the same things we've done for years.
I see what you did there, but I think he means "why should we have to remove it at all when we sit?" It's a mobile device, yet we're supposed to treat it like it's made to sit quietly on a desk without being used.
Sure, if I keep my iPhone face down on a table at all times, it's not going to bend, but I also want to be able to bring it with me because it's supposed to be convenient, not a burden.