You should probably be using masks sensibly even when they aren't mandated. If you're smart enough to get into university you're smart enough to learn when it's a good idea to wear a mask and what they're for.
1) There's decent evidence that masks can reduce the risk of transmission of corona virus (and other nasties) in situations where a brief task can't be carried out in a well ventilated space or can't happen with social distancing.
2) Masks have a limited lifespan especially if they aren't fluid resistant, as you use them (if you're infectious) you'll load them with virus carrying droplets which will eventually permiate the mask and be shed from it as you exhale. This takes a while to happen making them very effective at reducing the risk of transmission when used to protect each other during brief encounters.
3) Conversely it makes wearing the same mask for long periods less effective than wearing multiple masks only when needed because you are unable to maintain social distancing. I work in a health care setting and the guidance we are following is that our fluid resistant surgical masks should be changed either when they become wet or soiled, or after one hour of use whichever comes first. Fabric masks will vary but will likely have a shorter effective lifespan.
What does this mean for wearing a mask at uni?
In addition to following any rules your campus may impose you should also wear masks in crowded areas, areas with poor ventilation or during indoor meetings although you should avoid all of these if you can. But you probably shouldn't wear a mask around campus for the hell of it in areas where you don't have to, all you're doing there is degrading your mask for the high risk areas where you'll need it. Take more than one mask with you if possible.