A lot of teens aren't learning to drive in the UK anymore due to the high cost and quality of public transport in cities. So they by extension don't get a driving license until well into their 20s (if at all). So their choice was either, as you said, take out your passport (dangerous/impractical) or use a fake ID.
That's why they had to create the PASS scheme (Proof of Age Standards Scheme)[0][1]. In essence it is a non-driving licence/non-national ID card, card which only exists to prove your age. It costs £15, but that's still cheap relative to getting a driving licence (inc. test/cost to learn £200+) or replacing a lost passport (£72.50).
It is a good scheme.
[0] https://en.wikipedia.org/wiki/Proof_of_Age_Standards_Scheme
We knew the places which wouldn't ask, and it helped if you're tall
You and me both. I remember going out "in town" drinking and watching live bands from the age of 14, fake ID in hand. Pretty much all of my friends had them. Good times.
In the late 90s, when I was 16-17 and doing my A levels in the South East, plenty of people had fake "Prove It" cards and the like.
If you wanted to grab a drink at anything but the most desperate of pubs or go out in e.g. Brighton, you didn't have a hope unless you could prove your age.
Funnily enough, I knew plenty of 18 and 19 year olds that also used fake IDs, just because getting a more legitimate form of ID was a bigger pain than they could be bothered with - and taking your passport out seemed a bit over the top.
I dunno, maybe I just hung out with the wrong crowd?