Oh, there are so many factors in that decision.
First, when you say "should", do you mean morally or legally? If the latter, then they don't automatically get half. It's more complicated than that.
If you mean morally, then it's still more complicated than that.
For a start, how old are the couple, and how long have they been married? It is distinctly possible that, in the course of a long marriage, the expectation was that husband develops career and earns the money, while wife raises kids and keeps house. Even if a rather old-fashioned view, it's still quite possible, and the older the couple, the more likely. So .... the odds are that even if the wife had no direct involvement in generating a given fortune, she may well have sacrificed 20 years of earnings potential, but more than that, be old enough that it would be hard to now have the career she could have had 20 years earlier, so
future earnings levels would be badly compromised, as well as past earnings lost.
For example, suppose wife is highly educated, Oxbridge law degree, reasonably newly qualified barrister at, say, 30. Odds are she has a high-flying and high-earning career ahead of her. Then she gets married and, by mutual agreement, does the mother and housewife thing.
Now, 20 years later, can she EVER rebuild that sacrificed high-flyer career, at 50, with next to no senior experience? Had she stayed at work, she could well be a partner, company director .... or Prime Minister, by now. But, the prospects for future earnings, going forward, are a LOT lower than husband's. After all, he's got a current career, 20 years experience and excellent prospects, and she's effectively newly qualified with minimal experience, starting at the bottom .... if she gets the chance to start at all.
So, never mind past or current assets, what about future earning potential? His, with the solid career development, could be £500,000, while hers, as little more than a trainee, £30,000 .... if she can get a relevant job at all.
And that's just one aspect of it.
Another would be whether there are dependent kids? If so, who looks after them? And hence, who gets what in the matrimonual home?
Yet another would be that he has a career, and very possibly, a guaranteed substantial pension, ensuring a good income, on retirement. She, during 20 years of marriage, has a reasonable expectation that that pension covers her in her later years too, or perhaps ensure's surviving spouse cover, etc. But, after divorce, that's gone .... unless the settlement takes account of it, which it usually does.
Should she get half? It depends,
IMHO, entirely on circumstances. But she may well have given up a lot more than it first appears during the marriage, and have substantially reduced prospects in the future as a result.
Half? I don't know, but for a lengthy marriage, it's not an unreasonable starting point.