A first class way to improve the trains

Travelling from Paddington to Moreton yesterday I was forced to stand until Reading, as were many other passengers who, like me, had paid for the privilege.
Every carriage was absolutely packed to over-flowing. Well, not exactly. As an alternative to standing next to the lavatories (not a great problem, there, though - they didn't work) I decided to wander down the first-class carriages. There were four of them, only slighter fewer than the cattle class I was in.
I counted 54 empty seats in the two carriages I meandered through, so presumably there were in excess of a hundred vacant seats altogether - which would have provided somewhere to sit for every standee.
This is not a rant against first-class carriages. There is an obvious advantage for people who travel in them and if they or their employers are willing to cough up, why not? Hopefully it keeps fares down for the rest of us (not that we've noticed).
But why are there so many of them? If they are going to be two-thirds empty, which these were, why can't there be fewer first-class and more carriages for other passengers?
There is so much space in a first-class seat, with loads of leg-room, arm-room and every other kind of room, that no one could complain they were crammed in if someone sat next to them.
It is obscene that the rail firms take our money and force us into appalling conditions when so much space is left in another part of the train. Are they trying to make a point? To rub our noses in it?
The rail regulator (is there still one since Tom Windsor moved on?) should lay down rules that there can only be a certain proportion of first-class carriages in every train. Two in ten coaches is more than enough.