In my opinion none of these are good reasons for 128-bit computers, as they can be easily addressed by using 2x64 bit integers and software arithmetic, or bigin

In my opinion none of these are good reasons for 128-bit computers, as they can be easily addressed by using 2x64 bit integers and software arithmetic, or bigints. The issue with 32-bit specifically is that the maximum value (2 billion for a signed int) is really small and hits all kinds of practical limits: there are more humans than that! Whereas 2^63 is big enough for almost all practical purposes. There were costs to the 64 bit transition in terms of higher memory usage so I don’t think we’ll see another transition because the costs at 128-bit would outweigh the benefits.