What is the purpose of game introductions on this forum?

Do people read them?

It is mostly to garner interest in a subject, a system or a plot, it allows a gm to see if there would be interest in something he plans to run.  You'll find IC- Interest checks in here where someone has an idea, Input is just getting feedback, and advice is often for those who have a issue they can't resolve game wise on their own and would like to have others sound off on it to give them another view or opinion.

To my knowledge people do come here, and I have had games start from a IC.

Precisely that.

I did an interest check a day or two ago and there seemed to be enough general interest (and a prrference for one specific system over another) that I"m putting it together...

Since it's obvious some people read them because the forum persistently exists, I'll tackle that bit as "who": generally people who want something other than a generic D&D/Pathfinder game, the kind of game it would be worth asking if there are any players for before putting the effort into setting up. If you have something very common and likely to get players, there's no urgent need to IC, plus it's less likely those players will be around, because they can get what they like from Players Wanted.

In reply to tibiotarsus (msg # 4):

Just so.

I've also used this forum to get input about what sort of story and characters people have been wanting to play and have grown my game from their input. It's a very useful and fun place.

Also good for testing the waters to see if anybody else has purchased that brand new shiny game system that hasn't been out for more than three weeks yet....