They absolutely are in lots of ways. Phones are too small to be convenient PCs, but there's not much left they can't do these days. If you look at the spectrum

They absolutely are in lots of ways. Phones are too small to be convenient PCs, but there's not much left they can't do these days. If you look at the spectrum from phones, to phone-OS tablets (ipads or android tablets), to PC-OS tablets, to laptops, it's really not a solid line you can draw where things are dramatically different. The main difference is that the UX isn't designed to be good at being a PC.