Purpose- what to do? Why not just send message

I agree! It's a way of matching so people don't have to use one of the 5 daily messages to new people, but who in their right mind sends out more than 5 new messages a day or even 3 a day?.. how many people can you text with in a day or a week.
Basically it's a game.

"Nudge, nudge, wink, wink."

I guess it's a way to get someone's attention without saying hello

It's just an expression of interest, not to be taken too seriously.

I think some people send out quite a few 'nudges', wait to see what comes back, then decide if they are really interested in you. Someone who takes time to send a message, however small, seems more interested in getting to know you in my opinion.

yes