Students shouldn't go to cafés? The Washington Post weighs the question and points to a website that does the calculation: "a five-day-a-week $3 latte habit on borrowed money can cost $4,154, when repaid over 10 years."
How bad is that, really? You might easily blow $4,154 on a single vacation after college or getting a few extra options on your car. By contrast, it seems extremely sensible to buy years of a daily pleasure, which gives you some nutrition and focuses your mind and which gets you out of your little room or the library and puts you in a bustling, social environment, where you have your own little table and can get some good studying done.
A café is not just the coffee. It is an entire hours-long experience that contributes to your success as a student. It's true that to be financially savvy you have to realize that you spend a lot of money by spending a small amount of money on a daily basis, but there are much worse daily expenses that call out to students: bars, movies, cigarettes, fatty snacks.
I think the café-going student is operating at a high level, making a good choice. Do the calculation for yourself and think about whether Future You approves of that expense. I think the answer will be yes!