I dunno, that has merit. Students are less likely to have a driving license, and venues have Challenge 21/25 responsibilities. Most students are under 21. Therefore they need some ID and a passport is going to be the thing many of them will have. They wont want to be denied access whilst all their mates with passports get in.
Someone mine and your age certainly wont bother.
Venue does look to be skewed to the younger demographic - "Late Bar in the City Centre playing the best in RnB, Hip Hop, Commercial, Afro Beats and Funky House". It may be their policy to ID absolutely everyone.
In which case you should have asked to have seen a copy of their ICO accreditation.