Normal amongst the wealthy, financially incontinent or illiterate and those for whom it is their one little (big) treat (and who may not have thought seriously about the long-term implications).
£2.50 every weekday = £600 in 48 working weeks.
£2.50 every day, 365 days a year = £912
So you could buy a holiday for that.
Or save for a house deposit. £4,560 in five years, plus interest. Still a meaningful amount outside London.
Meanwhile you can buy bags of ground coffee for £2.50, which last 3-4 weeks for one person with a cafetiere. So £37.50 a year.
So, not just aspirational but actually preventing you from achieving other aspirations.
The bigger issue is that this is probably not your only treat. There might also be nice make-up, professional hair colour, more clothes than are really needed, nights out... just basing this on 20-something self and people I knew.
People should have fun in their lives, a lot of this stuff is not wasted. But you do have to pick your treats, otherwise you end up in debt, or with no savings when you find you need them.