Of course they do, if they've got a working setup. I haven't seen that Gulp is really any faster or easier to setup, so...

I'm way too young to be a grumpy old man, but I kind of wish people had just decided to learn how to use Make instead of re-implementing it over and over.

Webpack accomplishes everything you would need grunt/gulp for and is much more powerful. Grunt is essentially obsolete at this point

While true, that doesn't necessarily mean everyone needs to run off and learn Webpack. The treadmill of technologies in JS can be very exhausting so if Grunt is working for your project, why spend the cycles learning entirely new tooling?

Not sure why I got downvoted. I was legitimately interested.