Unless you're extremely wealthy, it's still half of what you had before though. It's still a lifestyle reduction.
Also low self esteem/pessimism/pragmatism makes them think they won't find anyone who loves them.
(I think women in particular think that because of their age. They are told by society they are not attractive or valued the older they are...(and while OLD does not entirely represent the world of dating, it does appear to demonstrate that aspect, women on here consistently report only men older enough to be their Dads contacting them on OLD when they are past eg 50). So I think they think they will have no partner prospects or very poor partner prospects.
You can see this in threads on here all the time .. .there's one on here from a poster who's discovered a past long term affair (and who has some indications he may be a serial cheat); one of the first things she mentioned in not wanting to end the relationship is that she feels she's now "old" and fat and will be alone. That she wishes she's found out years ago when it happened, she'd probably have left then.
On another post - not about an affair but about dating after separation/divorce, posters asked why the op was in such a rush/felt under so much pressure to get into another relationship esp. given she has young kids who would probably benefit from her not having a relationship & moving in with a partner ....she stated honestly that she wanted to meet someone while she was still comparatively young, because she felt the younger she was, the better her dating/partner prospects were.
I know a couple of women in real life who demonstrate that mentality too - dating and trying urgently to get into new relationships with very young kids because they think their prospects will decrease the older they get.
There are obviously women who, post divorce/separation, do go on to who meet men around their age who are good partners and whom they're happy with etc.
But I think the ones who stay (alongside other motives) rate their chances of doing so as too low to be worth the risk of leaving.