Why are men so unhappy at being single?

[Headaches]

I have a male friend (I’m female) known him since school. He has own home, good job, no kids, mid 40’s.
Hes had several long term relationships, every one after a few years either the GF gets sick of waiting for a proposal or for it to get serious or they get fed up of him and ends it.
The cycle starts again almost immediately then with a brief, intense grieving period but almost immediately he’s back looking for another relationship.
Ive told him to be happy being single for a while but he won’t.
Yet another GF has now broken up with him (she’s just grown out of love with him) and again he’s utterly devastated, can’t see a future without her, can’t go on etc but I guarantee within a few weeks he’ll be back on the prowl. Due to this desperation he’ll often get together with people who he really shouldn’t.
Its not that he’s looking for a cool and bottle washer - he lives alone but he just can’t be single.
Women on the other hand seem happy to be single and are comfortable with it. Why is this?

Any stigma is worse for women surely

Because some men are more needy than women and want a little woman to look after them, having been brought up with a mum doing everything for them or an ex wife who did, and they don't have the basic gumption, or are too lazy to learn to look after themselves.

I see this pattern more with older men/women.
Younger women seem just as desperate for a man ... any man ....
By your 40s+ you realise they just increase your workload, if you are a woman. So presumably women decrease your workload if you are a man.