I've often wondered the same thing; you'll find us wherever 'things' are happening--concerts, live chatrooms, etc. But when we're not "doing" things, we can be difficult to spot. Oftentimes, SP's will be the ones who will drop whatever they are already doing (even working) in order to do something exciting.
Incidentally, I haven't found as many SP's that are as into Typology as other, more 'cerebral' types would be; I've found most SP's tend to take typology for granted. (The only reason I myself don't is because, being mildly autistic, it helped me figure out why my, ah...'intensity' made most people want to run away screaming. xD; )
Some of us may also be mistyped; certain parts of our society don't really approve of Se-based lifestyles, forcing us to often develop parts of ourselves that we feel we need to display in order to not feel like we're about to be crucified. For instance, when I was on my SSRIs that blunted my ability to enjoy myself by living in the moment (I was prescribed Zoloft in order to deal with my horrendous PMS and raging depression with being a crummy planner, and wanting to live the life of an ESTP, yet not being able to due to having hyper-protective xNFJ parents that apparently operated under the maxim "OMG I must protect my baby so she doesn't melt down in public and embarrass herself!"), I acted more visibly like an INFJ; I thought it was what was needed in order to make me look 'smart' or 'alluring' in the eyes of my peers. It wasn't until after I went off of them and "tore down the wall" that I started growing more independent and consequently realized that NOT being an ESTP was making me feel even worse.
Also, I will admit my wordiness also tends to make me come across as more of an N than an S; this partly comes from being called "stupid" and "crude" one too many times as a child, and developing my vocabulary to better 'sell' myself as an intellectual. xD