What is the benefit of fat tires on pavement? This year in my area, I've seen a lot of people using fat tires on paved bike paths and roads, when there was no fat bikes before. I also see a lot of these bikes in grocery stores. It is summer, so there is no snow.

I'm curious of the benefits of a fat tire beyond the obvious off-roading capabilities. Is it just a weird fad or is there some benefit of a fat tire vs a hybrid or a road bike?
What you're witnessing is probably a mixture of convenience and all-around-increased popularity of fat bikes, rather than actual 'benefits'

A lot of people don't have the luxury of owning multiple bikes: one for the road, one for grocery trips, one for cross country, etc. If someone only has the resources for one bike, and they chose a fat bike because they like the versatility, you can understand why they would take that bike to the store. It's easy to argue that a fat-bike can go off-road, on the snow and sand, and of course to the store. A road bike cannot do all of that.

Also, wide tires are generally more comfortable. I could shed some weight and increase my speed a little by running ~30mm tires, but I choose to run 40mm tires most weeks because they handle bumpy roads and gravel with comfort and ease.