Taking pictures specifically for a dating profile would show that they actually care about finding a person they would do other things specifically for.

This is a dead giveaway that you've never asked men why they don't take and share pictures of themselves. Most men in the anglosphere consider it vain and self-destructive to obsess over their looks. You can also see it in the way they buy clothes ("I'll take 5 pairs of the same pants, thanks"), the way they cut their hair ("just take an inch off and even it out"), and the way they present themselves, often with as few accessories and adornments as possible. Those they do have are utilitarian or deeply personal.

It’s that men don’t take a lot of pictures of themselves.

I can't speak for all men but I have a complete inability to look even remotely normal if I know a picture is being taken of me. I try to take profile pics and they all wind up awful and that's not just my view. I showed my friend just to make sure it wasn't just poor self image talking and they reacted like I was showing off a broken bone. I think the only way I'm going to get workable dating profile pics is if I have a friend take pictures of me without me noticing like I'm some sort of cryptid and they'retrying to capture proof.

I just don't want pictures of myself on the internet. I value my privacy. Huge part of the reason I never had a dating profile.

Unfortunately, the fact that they don’t take many pictures of themselves can be really obvious. I try not to turn a guy down because of a bad profile picture, because I know there’s a technique to it and that requires practice.

At the same time, we’re in a digital era - you can take 100 pictures and only upload your favorite one. There’s no reason for an average guy’s profile picture to resemble a mugshot.