The difference is that PCs and PC-based servers really can do everything mainframes can do if you port your software. Phones cannot do everything a PC can do, b

The difference is that PCs and PC-based servers really can do everything mainframes can do if you port your software. Phones cannot do everything a PC can do, both for hardware reasons and for OS lock-down reasons (the latter is a bigger barrier for iOS). The mainframe/PC = PC/mobile argument is a piece of faulty reasoning by analogy. PC/mobile is more like truck/car than horse/car. Cars displaced horses for transport, but cars do not displace trucks. What we are seeing is specialization. Phones are used for short transactional interactions with larger systems, texting/chatting, and casual reading. PCs are used for more prolonged deeper interactions including virtually anything creative. The latter may seem smaller than the former when you go by usage logs alone, but the latter is more important and is not going to be displaced unless phones can grow to do everything PCs do. In that case you no longer really have a 'mobile device' in today's mold. You have a tiny form factor ultra-portable PC that can be used as a phone when not plugged into a monitor. Going with the car/truck analogy you might say that prior to mobile there really wasn't a "car" in computing. There were trucks used as cars, but nothing truly ultra-portable designed specifically for lighter more casual interactions. Mobile exploded because it filled a missing niche. Note that mobile hardware may "eat" PC hardware in the sense that ARM64 could eat x86-64 eventually, but that will be an ARM64 running a PC OS. It'll be a higher clock speed ARM64 with more cores, more cache, and more cooling too.