Who thinks it's okay to sit on their phone?
You can flip this around and ask what company bases their product on theoretical ideas about how people ought to use it rather than watching the way people actually do? I don't think it's sensible to drop a phone in water, but that hasn't stopped companies from making phones that are water and drop resistant. People in the real world also tend to put their phones in their back pockets, especially bigger ones that may not fit comfortably in a front pocket, and that inevitably means they get sat on. A company that makes a phone that's likely to be sat on needs to make it durable enough to hold up when that happens, or they'll be rightly criticized for failing to produce a quality product.