Completely agree with the OP and many others on here.
As someone said further upthread, many men who are single past 40 are single because they have cheated, and/or they are a nightmare to live with and lazy and entitled etc, and their wife has kicked them out. So this is what many of the men looking for a woman are going to be like.
I heard one woman say the other week, that they went on a date with a man they met online, and the first thing he asked is 'can you cook?!' 
All many men are looking for is someone to wait hand and foot on them.
The women who are single are women who have got rid of men like this, and have licked their wounds after a few years, and come out looking again.
And it is true that many men seem to want younger women. And it is so so so hard for any woman over 45 to find a decent man. I am so glad to be in a LTR (married nearly 30 years,) and would not even attempt to try and find someone else if DH left me or died. (And I couldn't be arsed anyway.........) Because women have such a hard time trying to find love/a relationship past 45.
This is why it makes my bloody blood boil when I see people say 'leave the bastard,' 'plenty more fish in the sea,' and 'so WHAT if you're 52, you're just a wee spring chicken - most men will be banging your door down for a relationship with a woman who's hurtling towards her mid 50's!'
I said something like this the other day and got shot down in flames... but it's pretty true, and I don't think it's offensive to say it.
Why do some people on here act like an age like 50-ish is 'nothing' and that they know women who look 30 at that age, and who have a gorgeous and fit young professional man who treats them like a princess!
Fact is, many men are not looking for a woman past middle age when they are on the hunt for women. Not even past 40 usually.
I am not being mean; I am in my mid 50's myself, and I KNOW I would struggle to find a man now. I am chubby (size 18,) I have an average job with an average salary, average qualifications, and very little savings to speak of. I am going grey at the temples, I don't have the fit figure I used to have, and I haven't had a wolf whistle in 20 years.
I also haven't been chatted up by a man in 20-21 years. They are courteous and friendly to towards me, but never romantically interested in me. So I know if my DH left me, I reckon I'd be lucky to get a man at all!
As I said though, I wouldn't want anyone anyway. I just couldn't be arsed with the hassle of a new relationship, and trying to get used to someone else. I am too set in my ways, and although I love DH and he loves me, I couldn't be arsed with anyone else..........
The people who think women can get a man 'just like that' are the same people who think you can retrain for a new career at 53, because 'you're just a spring chicken,' and employers are going to be banging the door down to employ a 59 y.o. woman with an open university degree she took 6 years to get!! And of COURSE it's perfectly acceptable to start having babies at 46. I know loads of people who have done it.' hmm Mumsnet is like a parallel universe sometimes.
As I said, I am not age bashing - I am in my 50's myself, and I can tell you it is NOT a 'young' age to start over. I know some people will come out with a story of this person and that person who met 'the one' at 59-60' but to be honest that is the exception rather than the rule.
Hope I haven't offended anyone. And I do think that women who struggle to find a man after the age of 40-45 should not beat themselves up or think they are 'CHAFF' 
it's because it's so so so hard to do! Many 40+ women I know are amazing, funny, sexy, intelligent women, but men of roughly their age, want a Holly Fucking Willoughby lookalike who can cook and will shag them 10 times a week! 
Not been single for 35 years, but I do empathise and feel for the women who want to be in a relationship, and are single (long term, and into their 40's...)