Surely there aren’t enough people walking them constantly to mash the grass to death, is there some kind of membrane placed under the dirt to stop grass growth?
Here is a pic of worn path from walking on, rough edges, clearly not intentional.
Will post pic after walking the dog of the trail that I’m speccifically curious about.
I should clarify that my original comment – foot traffic keeps paths in decent shape – was in answer to the OP’s titular question, about why vegetation doesn’t grow atop the intended walking/hiking trail. But you’re right that traffic will cause other impacts, even if plantlife isn’t getting in the way.
I’m in 100% agreement that for trail upkeep, people have to be mindful how they step. The advisories here in California focus on not eroding the edges of the trail, such as by walking around muddy areas, which would only make the restoration work harder and damage more of the adjacent environment. We have a lot of “stay on trail” signs. We advise people to either be prepared to go right through the mud – only worsens an existing hole – or don’t walk that trail at all.