The point about large word lengths is you get higher data throughput, and faster processing, because everything is going through fat pipes into a big parallel machine with multiple levels of cache and vectorisation.

The issue is the utility of floats at different precisions. 128-bit floats have some benefits for high-end scientific applications, but the extra cost and complexity over 64-bit hardware would only make sense for specialised scientific supercomputing. So far it just hasn't been worth it.