I think the problem with MUPs in some cities is that the planners think it is a good idea to locate them in scenic areas, around parks, along rivers, and other enticing places that make the MUPs into recreational destinations.

Where I live the MUPs go through industrial parks, warehouse districts and along utterly shadeless marginal areas along highways and water diversion channels. In some places they go through neighborhood alleys and here you see the occasional dogwalker or fitness walker, but they are mainly used by commuter and fitness cyclists (and homeless guys and little gangbanger wannabes. Ah, there's the rub).