While there is an "uncool" aspect to them, the reason they are much less common now is because wide bars make them less needed and less useful.

I loved my bar ends in the late 90s when I was running 560mm wide bars. If I wanted to stand an hammer, they gave great leverage on climbs.

However, as I went wider with my bar, I noticed I was using them less. For one, the wider bars just made me need them less, and when I did try to use them, they were too far apart. Now I am at 750mm, and they would feel very awkward to use at this point.

Now, for a flat bar road bike, where I might run a narrower bar, I would likely put bar ends on them.