Shopping,
I just assumed bochurim weren’t put up to such standards because you always see them making some sort of music video in the street, running late for minyan, or something else that they technically are allowed to do because it isn’t assur to have girls look at them.
To throw a monkey wrench into this my shul’s rav said there is an opinion that it is assur (don’t remember who it was in the name of) and the proof is from shaul hamelech