I think a lot of guys in that age range play primarily fours because that's what was available when they were starting. By the time 5'ers came along in full force these folks already had "their sound". However, as already noted, Marcus and Victa play 5'ers, as well as Nathan East and others. (Nathan plays 6 strings too.)
I think it's all about the extended range you get with 5'ers and 6'ers, and most importantly how you make it work for your style of music. But, if these cats can make their 4-string axes sing, then it's all a matter of preference and not of superiority of any kind of bass.