I've used them in the past. I even enjoyed using them. But they have fallen out of fashion for a couple of reasons. The first reason is that the cheap knockoffs gave them a bad name. The Grab-on version is stable to UV and doesn't degrade very quickly. The cheap knockoff versions weren't. They degraded into a crumbly mess that most people don't want to deal with.
The second reason is that they aren't all that compatible with modern brake and/or derailer cable routing. They were something of a bugger to get onto the bars as it was. Trying to slide them over one or two pieces of cable housing won't make them any easier to put on. It can be done but it's easier to use tape.
I still use the mountain bike grips and I prefer them over just about any other grip I've tried. But I just can't see using them on road bike bars. Not that I think they are unnecessary or they aren't useful, I just think they are too much of a hassle for use with modern bikes.