Unless he is physically abusive and hiding the money, a lot of older wives will stay because....
...they don't want to become like the whores who are sleeping with the husband.
There have been plenty of women who swear they don't need a man, until they're divorced/widowed and the loneliness becomes unbearable. That's when they'll open up to anything and find themselves getting into situationships they swore they'd never do.
It's especially hard when they see the ex-husband moving on and remarried. Nowadays, it's even easier for the men when there are plenty of mos ab just dying to come over and throwing themselves at the men. Imagine you're an aging divorcee who was hoping the guy you've been sleeping with, spending time with, cooking for, opening yourself to, and even nursing his ailments, just won't settle down with you, and has in fact, been pulling away for the past few years. When you confront him he accuses you of pressuring him and being needy. Meanwhile, your ex-husband is remarried to a mos ab. They're taking vacations together, attending family events, celebrating with the kids, etc. and sharing all of this on Facebook. You have nothing to share on your page because you don't actually have a life with anyone. What you have is a handyman willing to do favors, but only if you initiate.
Personally, if the husband isn't the one trying to leave the marriage, it almost seems like it's to the wife's advantage to stay. Older guys are too used to their independence, and if they were looking for a wife who is closer in age, they are looking for a hospice wife. But if you're willing to be the hospice girlfriend, that's an even better deal for them. You'll be hard-pressed to actually find real love.