We had that in my local park. There was a huge field that everyone walked through because it was much quicker than going around. So they finally made a sidewalk there (not with tarmac though, more like gravel and sand mix). Just a couple of weeks later there was a new path just parallel to this one. My guess is the problem was that the field was a bit hole shaped (sorry I don't know a better term in English) and this, as well just the nature of the sidewalk, led to it accumulating water puddles, and also it just turned into sandy/stoney mud when it rained. For bikes it was also just more comfortable to ride over the grass than over gravel. But it still felt like an asshole move.