I think the problem is assuming that the men are “in the wrong” and behaving badly- some will be, of course. But it could be that what your DD and her friends are looking for is not what young men of their age are looking for right now? I imagine that many men at the younger end of that age spectrum are not looking to settle down, and perhaps the majority of those that are looking to do that have already done so. Neither is wrong, just looking for different things.
Most apps are realistically more likely to be used for finding casual sexual partners. I asked my DD and her friends- both said they wouldn’t rule out having a relationship with someone they met on most of the apps, if they hit it off, but they primarily think apps are where you look for hook-ups/casual relationships.
Most young men I know well are either in long-terms relationships or focussing on work and/or hobbies.
I asked one who is here right now your question- his answer is that he finds women of his age looking to be in serious relationships want quite a lot of commitment, reasonably quickly. He feels they can be quite intense from a very early stage, and seek quite a lot of reassurance/ demonstration of commitment to them (e.g. over friends/hibbies/previous commitments) after a very short period of dating. They don’t want to “waste their time”- as he has had it out to him- and want almost promises of approximate timeline/future plans. He says those women aren’t really happy to go with it and see what develops as they get to know each other. He is very into his chosen sport (many of his friends are also into this), which he does to a high (though not professional) level, and does not want to give up time doing it at the moment. Mainly because he won’t be able to do what he does now, to that level, forever and he wants to make the most of it whilst he can. He also works quite long hours and between that and fitness programme he has to follow, there isn’t masses of time left over. He absolutely accepts this limits the dating pool available to him to those who are also very busy/happy with a casual relationship and “see how it builds” and more casual hook-ups. He says if he met someone who he did fall for, then maybe some of that would change- but right now it’s not something he is looking for or prepared to make lots of compromises to find. I can see both sides- why waste your time if you are 100% sure you want children, but the man you have started dating does not, for instance. On the other hand, at 25 years old I had ideas about what I wanted but plans changed- some by choice, some from necessity and flexibility is important too. I think going in demanding curtailment of hobbies/significant compromises after only a few dates, for instance, is a bit odd.
He thinks the women he meets casually understand the situation and he isn’t trying to pretend about what he is looking for/able to offer- but of course he is “nice” to them when they meet up. Not because he is trying to pretend he’s looking for long-term relationship, but because it would seem pretty odd to meet someone you are hoping to have a bit of a fling with- or perhaps met on an app and it’s clear this a one-night thing- and be anything but nice, charming etc. He said that he doesn’t ghost women, but he says there are a couple of times he thinks it has been very clear that he is not looking for anything serious, but the woman would like it to be more and he has cut contact when they’ve been persistent. I suspect, as with most things, there will be times where one party is at fault for miscommunication/wishful thinking/downright dishonesty and times where both parties are in the wrong.
So, I would guess it is a mix of factors: some young men not being ready to settle down, whilst your DD and her friends looking for a different type of relationship; those young men who are wanting to settle down already having done so; a proportion of men better off being casual hook-ups only (or avoided, if casual sex is not something you are comfortable with). I doubt they are all “just after one thing”- though of course there are some men who will be unscrupulous and I suspect many might be happy to have sex with a young woman who seems keen without too much thought of her longer term plans