Can I offer an opinion on the subject?
Bad boys- and I'm referring here to the attractively naughty ones, not the dickheads - are confident on the outside and wounded on the inside. Their wounds cause them to behave in risky ways (in my job I describe this as "maladaptive health behaviors to manage negative affect"), and the confidence is a shell to protect the squadgy bits in the middle; like chitin on a cockroach, it makes them virtually indestructible, but no less messy if you somehow crush them. Women are drawn to the combination of confidence ("chicks love confidence," as Minnie Driver tells us in the South Park movie) and vulnerability. Women will, indeed, tolerate a surprising degree of dickwad-ery in order to feel that they and only they understand and can HELP this beautiful, wounded soul.
All of which, needless to say, usually ends badly.
Nice guys, in contrast - and here I mean the kind of nice guys women don't date, not beta heroes - wear their insecurity on the outside, like a particularly unwaterproof raincoat. A protective layer of nothing, with nerves (as PG Wodehouse might put it) sticking out a yard from their bodies. You can't touch them without hurting them. So you don't touch them.
This also ends badly.
Fortunately, I think, most people are reasonably healthy and able to tend to their own, not-too-abundant emotional needs. I think most of us live in a happy middle-ground between self-parenting so fiercely that no one can get close to us and needing so desperately to be parented that no one but an actual PARENT would be willing to do it.
In other words, I think most of the time this isn't what dating failure is about; I think most of the time dating failure is about simple incompatibility, without reference to the emotional health of the people involved. Most of us are reasonably good at staying over our own emotional centers of gravity and, like, being nice to each other.
And if you find yourself leaning on the tired old trope of "He was/I am too much of a 'nice guy,' to go out with," or "They/I like me/him because I'm/he's a 'bad boy,'" there's almost certainly something more interesting happening that you'd be able to see - and probably learn from - if you stopped to look a little more closely and think a little more critically.
Like culture has fabricated these boxes into which we chuck people - the Bad Boy box and the Nice Guy box - based on the flimsiest of information, and we think we've EXPLAINED something, when all we've done is... put it in a box. It's not that the bad boy/nice guy trope is without ANY meaning, it's just that the meaning is so rarely useful and so shallowly descriptive as to make it almost meaningless.
Me, I think you can do a lot more with a gender-free story about self-care and empathy.