The comfort factor. The tables are tiny. Yet, I find that cozy chairs make up for that. Students stand in line for the oversized armchairs. I love the local artwork hanging from the walls and the seats arranged next to windows.
Some people park themselves at the choice tables for hours.
Luckily, not all coffee-shop students are so fixed. Study-group students are a more transient bunch. They'll meet to plan next week's class presentation or cram for the following day's midterm, then leave. I often catch a space as one of these groups packs its bags. The Grade A tables are available, if you're smart about snatching one.