Is vpn necessary while using campus wifi?
I don’t think you’re aware how a VPN works. You mentioned a fear of being hacked into in another comment. That is very difficult via a network like UCSDs, unless you’re constantly transmitting unsecured packets, which is very rarely the case with 99.99% of sites you visit nowadays being HTTPS.
The only reason you would need a VPN on school wifi is to protect yourself (privacy)-- as the University of California logs & processing every site you visit, and we don’t quite know what happens to your info (like a conventional ISP)… so if you don’t want Chancellor Khosla knowing you watch spicy videos at 3 am before a final, use a VPN… He would be so disappointed. (Note: People don’t actively monitor your traffic, but can if needed.)
Another reason you might want to use one would be if you ever wanna get any content via less-than-legal manners (e.g. textbooks, software, movies) so that ResNet doesn’t send you a warning for doing so. (This only happens if Resnet gets a cease and desist.)
The last reason would be if you want to watch content available in another country on like Netflix or something. Other than that, no real reason to. If you do decide to go for a VPN, make sure you do your research and don’t purchase some shady one 
No, it is only used to access resources such as the research papers if you’re not connected to campus wifi
What about ppl trying to hack into my laptop or something like that?
Oh I thought you were talking about UCSD’s VPN (can be accessed through AnyConnect at vpn.ucsd.edu). UCSD-Protected is pretty secure, as it uses SSO credentials along with WPA2 security. As long as you aren’t torrenting (which is illegal), UCSD-Protected works fine
if people are going to hack into your laptop it is going to be because you opened the wrong link and downloaded malware or didn’t keep your computer updated properly. the campus network itself is safe