In a nutshell...
1) The women are from various walks of life...reality shows, wrestling, playboy, etc
2) There is money to be made in these...I don't collect them persay but I do have a bunch of them, from busting various products over the last 3 years...when its a new product, it has a lot better return rate, but even on older stuff like 2011 vault, I was averaging about 75-110% back on on investment, and this is with me only buying boxes here and there, not cases...yes, you will get some bad boxes, but you usually come out a lot better than in any sports product
3) some girls are more sought after than others, just like in sports, so a auto #/5 of Jessica Burciaga is worth more than an auto #/5 of Tanea Brooks...just like Jeter auto is better than Ryan Theriot auto.
But to the OP's question, why do people collect cards with actors on them or baseball players on them??? same thing really...
not sure what you're using as your key words on ebay if you're getting benchwarmers though...
Not looking for anything specific...usually will just looks through buckets and lists to see what catches my eye.