People who walk on grass (to shortcut 5m of path), men who wear hats indoors, men who shake hands limply and/or sitting down, people who say no to new experiences or 'I don't like that' having never tried.
Planners who don't put the paths where people are obviously going to want to walk. Apparently when York University campus was built they didn't put the paving in until the pedestrians had worn paths in the grass.