--although many overlook the fact that half of the wealth was their partner's.
Most of the wealth of a married couple who own their own home is tied up in the home. Unless one of them can afford to buy out the other, they will need to sell (and will tend to need to take an early, hence low, offer), which will be considerably less than they could have expected to get if the sale were unforced, and probably dramatically less than they might have anticipated it's future worth to be.
Add to that the costs of then acquiring a new home (x2), in which lawyers, agents, bankers, and insurers all take their cuts, and it's a very expensive business.
Did I mention I have actually done this;
Twice? I'm inclined to take my actual experience as more valuable than your guesses about how things might be in theory.