R.C., I'd agree with you that you usually wouldn't need them. I like to send them when sexting is happening and it's going to be a few days before we can meet. Some girls like a visual. The typical transaction for me is about like this:
Me: I'm going to get naked and shower
Girl: Have fun
Me: **Body pic in the mirror showing my tattoos, and not showing my dick, but only a hint of it**
Girl: You shouldn't tease me
Me: Get your mind out of the gutter ya lil perv

Girl: You sent me that pic!
Me: You liked it, don't lie, dork. Send me a pic, leaving me hanging jeez
Girl: **Body pic usually in a bra or tank top* **Sometimes a shirtless pic**
Me: Damn hottie you're making my cock fucking hard already. FUCK
Girl: Oh am I?

Me: Yeah now who's the tease?
Girl: Show me!
Me: I'll send you a picture of what you're doing to my cock, but this is quid pro quo

Me: **Dick Pic**
Girl: **Shirtless pic**
And it goes on from there. If they're willing to send me pics like that, then it's certain that all I have to do it get them to the house and fuck. Very little work on my part, and some stock dick pics that I have, which I tell them is what they're doing to me right then. Women want to be desired. Hard dicks FOR THEM turn them on.
Also, I usually use a dick pic on a girl I've pulled my "I'm not most girls cup of tea..." and "I'm kind of a filthy fucking man whore, honestly. It seems a lot of girls don't like men being that honest. I'm just up front. What can I say" type routine on. I don't pull that routine with all of them but I do use it a lot. If they bite into it then I'll send a dick pic. All this does is establish a rapport that I'm a fuck machine and I can be an option for them, and they get a visual, and I get pictures in return.
Dick pics can be okay.
Like I said I really rarely use them, but I do use them when the situation calls. I'm a big fan of text game, and dick pics can be a part of it.
The best use of the dick pic I've had:
I never sent a dick pic to this girl. We met up at my house, we fucked, she's awesome. Becomes a good fuck buddy (she still is right now). I sent her a dick pic like two weeks ago just for fun (after we had already had sex a few times), accompanied with the text "thought you would want a dick pic since we know each other now." She laughed and said "Thank you I like it!" which was probably bullshit, but whatever. But here's the cool part. If she's horny on a night she doesn't get an invite, I now get a picture message from her, usually showing her big perfect tits, biting her lip looking at the camera. We never exchanged pics like this before. So when I get one of those pictures, I snap a dick pic and say "I'm home." Five minutes later my door bell rings (she lives really close). This has been going on for about a month now.
EDIT: ^^^ By the way, that girl is a solid 9 by anyones standards. Thin, fit, big perfect tits (no sag), thick brunette hair, glasses, perfect skin, insanely tight vagina, nice little round ass, perfect teeth, thick lips, doe eyes. Past looks, she's a wonderful person, a bonafide genius, friendly and outgoing, laughs all the time. Just a wonderful girl all around.