Why do the spouses of celebrities get so much money in the case of divorce when it's clear they wouldn't make near so much money had the relationship never happened?

Many years ago almost all families were simple: a man and a woman would marry when fairly young, and then the husband would get a job and go to work and the wife would have children and stay at home looking after them and doing housework.

If they got divorced the woman would be in no position to work: she would have no work experience, little education and she would be in a society where women working is unusual. What's more she would probably still have the children to look after. It made sense that the law protected the woman in this situation by giving her half the accumulated property from the marriage and half of the future income of the ex-husband. Half seems like a sensible amount, maybe even stingy, because she spent as much time working in her role as wife as the man did in his role as husband (maybe even a lot more), and it wasn't like she chose this split of responsibilities anyway.

That's why the law was written the way it is, but why hasn't it changed?

One reason is that there was never a defining moment when woman were suddenly considered equal to men and were able to get jobs as easily as men. Arguably this has still not happened.

Another reason though is that if someone stays at home to look after children (man or woman) then they are still contributing to the marriage, and if it ends have a right to some of the household income from that time. What's more they have a gap in their work experience, and may want to continue bringing up their children, so getting a new job at the level they would have if they'd never married would be difficult or impossible. So they have someright to the future income of their ex-partner.

How much is this "some"? This is a very tricky question, and it would have to be answered by politicians writing new laws. Politicians don't like tricky questions, because whatever answer they choose it will make some people very angry. Leaving things alone (or putting the question off) tends to not make people so angry. So politicians just ignore the problem, because it's easier.

(One last thing is that the law was also probably not written with the excessively super-rich in mind, although I'm not sure why since very rich earls and suchlike did exist.)