According to a study conducted at the university of north carolina, one reason that college students feel so much pressure to drink is:

The reason why college students feel so much pressure into drinking is because they believe that drinking is already normal to them and by that, they have the thought of it is normal that they feel pressure to drink especially in situations when they go out with their peers or social situations. Especially when they see their friends drinking and they're not, peer pressure would likely take place, persuading them to drink and have the idea that it is normal and they should do it too.