The 'Mumsnet community' are real people who are out there in the real world and in real communities. We're not sequestered here.
As comparable examples, in my community it's quite a rarity for women who marry to change their names. Anecdotally, there was a swing away from this in the nineties and noughties but the pendulum has now gone back the other way. In my circle it's stayed the same, but in this case, it's likely the community who are the anomaly, not British society at large. We can't assume that everyone out there is just like us.
This is the usual ebb and flow of social trends as dictated by time, as well as demographic. A deep tan was very fashionable in the 80s but has now fallen out of favour, as the beauty industry may well see in the future on grounds of sustainability or covering the body in potentially dangerous chemicals.
It may be that particular demographics embrace particular trends at particular times, or that specific demographics prefer specific ones at the same time. And the class snobbery you see on here is by no means confined to Mumsnet. It's a particularly British (and very annoying) hang-up. It's also a very real barrier; a construct of tangible glass ceilings for a great many people irrespective of their level of education and competence (or of whether they have gel or acrylic nails or not).
The question you asked was whether we, as MN members, get our nails 'done' for holidays.
People simply answered it.