Because the majority of the British public are shit at saving and will continue to just keep putting stuff on a credit card rather than cutting back. It's very hard to stop treating yourself to things once they stop becoming luxuries and you get used to thinking of them as essentials or bare minimum.
It's exactly the same as 2 years ago -according to the news EVERYONE was struggling for money due to furlough not being equivalent to full wages, some people not being entitled to it, others losing their job - yet in the real world pubs and restaurants were bursting as soon as they were allowed to reopen, everyone and their dog was spending a fortune on hot tubs, garden furniture etc.
Also bear in mind that lots of people weren't having their usual holidays for 2 years- in 2019 the average brit went on 1.9 holidays abroad, so when taking into account the very poorest and thise who wouldnt have gone abroad that's an average of 4-5 holidays saved per person which if you're used to spending a few grand per holiday is a lot. Millions of people are still working from home, saving thousands a year in commuting costs. Some people have done really well from house prices shooting up. I, my parents, and a few of my friends are all still on our fixed term energy prices so the increase hasn't hit us yet. Etc etc.
Basically the cost of living will hit everyone at some point, but some haven't really been affected yet, some will have enough of a buffer not to have to significantly decrease their non essential expenditure, and some really should decrease their spending but won't because they consider they deserve it, life is for living, they'll pay it back at some point, their wages might go up or they will get an inheritance or make a profit when they downsize their houses, etc etc. There was a thread on here about a month ago where a poster was wondering whether to make a big non essential purchase with no guarantee she'd ever pay it off and 70% were encouraging her to go for it on the basis of the arguments above.