Yes, salsa crowds are much younger. I have a lot of friends who have turned salseros/salseras. When I ask them why they quit tango, all their answers have the same theme... "Tango is so hard, and takes too long to learn; Salsa is so easy; There's a beat we can follow; It's happy, tango is just so intense—we can't handle it; The contact is too close; etc."
That's why (IMHO) the salsa crowds is younger. Lack of patience, and geared more towards instant gratification.
I totally agree Amstper, (imagine that.).