But there usually aren't any spare seats at the tables once the families have taken them - these are coffee shops with tables for 2-3. I do ask I'd there is space but very often there isn't. And people grab all the spare chairs around to make bigger noisier groups that aren't easy to join.
I could just get takeaway and sit on a bench, but there aren't many, it's messy and cold, and I do quite like to sit in the cafe on my own for 20 min reading the paper and having my coffee. It's my chance to get out of the house and be around people!
But it's not a black and white thing. I agree that in a group, I'd probably do much the same thing, though I hope we would wait til there was obviously more space. So I totally get the reasoning behind it, just find it frustrating when I'm left standing. It's not a problem with an easy solution given the sort of cafes there are around me, and given how very busy they are ( and often how filled with students for hours in end).
So I don't think people are being unreasonable some of the time, though I wish they'd look more at the size of the queue or notice that if people are standing around with drinks and their teenager sits waiting at a table for ages while they're I'm the queue, they could suggest they move or share or something.
And it depends loads on the sort of place it is and the frequency of turnover and just the sort of customs that have built up.