and even if wifi supported roaming, there would be the issue of ipv4, as most wifi routers are NAT-ed these days, meaning you may well encounter the same ip on multiple connections (what roaming is, in a basic sense) and have no idea what connection to use.

hell, the whole internet infrastructure is built around the concept of fixed connections. that one can roam with a mobile phone today is just because your roaming within a single supplier so that they can attach a ip address at their end to whatever internal address your phone have, and make it seem to the net that your phone is always connected at that ip.

ones one start roaming multiple, non-synced networks, all that goes out the window, unless one have ipv6 and can allow every single device to have its own unique ip, and some very complicated routing tables (vs today where one can get away with reading just parts of a ip address, thanks to subnets).