Coffee Stain on Teeths, bad breath, but most importantly, it saves money. In college is common to see people unable to focus without coffee, and crave constantly before a study session, I do wonder if the habit of drinking coffee could be harming the ability to focus without it

I'm sure there are a lot of studies about coffee, and I completely agree, that they improve focus, but the withdrawal could be more harmful to concentration than without it (e.g the person who doesn't drink caffeine could had better baseline focus compared to folks on withdrawal)