Standards change. The thing I like best about 31.8 is that finally road and mountain/hybrid stem sizes have found a matching standard, until the next one comes along. What this means is that pretty much any stem will work with any bar drop or flat, for now. I could take the stem off my mountain bike and use it with the bars on my road bike if I wanted to. Also, it has been said by manufacturers that 31.8 bars are stronger, yet lighter. In the past, when I was young, soon after the earth's crust had cooled, it was recommended that handlebars with those wimpy 25.4, 26, and those oddball 26.4 diameters be replaced on a regular basis due to fatigue caused by those "tiny" bars. I have actually broken 25.4 bars more than once, so it must be a thing, nothing to do with the fact that I bought the least expensive bars I could find. These days I ride in the full knowledge that my 31.8 bars on my road and mountain bikes offer me complete security