First the A comes along so that when the police show up you can claim "They said they were 18"
Then the S so they don't make the mistake of pm'ing a guy.
Last comes the L so they can decide if this is someone that lives close enough to bypass the cybersex and go straight for the hookup.

I think it is mostly a way for dudes that are wanting to get their rocks off to target perspective candidates.

Teddy... I think the ???'s you mentioned come across with more of a "Hey, let's actually converse" vibe. Way better than a/s/l.

__________________
Put me on wheels and I'll turn tricks.

Clever? Nah, I ran out of that years ago. But if you find this, let me know, k?
"The road goes ever on..." ~ Tolkien

In memory of my friend skip...
Go then, there are other worlds than these