Okay, this will sound super-cynical, and before I get flamed, it OBVIOUSLY DOESN'T APPLY TO EVERYONE WHO OWNS A STROLLER, but here goes...
If you have a baby carrier, you don't get the materialistic "fun" out of buying a stroller.
Think of it: Though some baby carriers can be expensive, they're basically a length of cloth, whether we're talking a didymos (enormous length of cloth), Maya (cloth with rings), or rebozo (Cloth. Just cloth).
OTOH, a complete Peg-Pérego "travel system" not only comes with its very own accent (é) and hyphen (-), which of course ups the pretentiousness factor by 10% for every relatively unnecessary diacritical mark, but also is wildly bulky -- the advantage of which is that you announce to the world that you, too, have purchased something BIG, but has lots of gizmos, pockets, and places for you to put -- you guessed it -- more stuff you buy. The bigger and more elaborately expensive the stroller, the truer this cynical observation of mine here tends to be, so the people who buy the little umbrella doll strollers don't tend to fit this mold very well.
I can't tell you how many times at the mall, I've seen the big baby carriers used basically as an expensive Italian shopping cart while Grandma holds the baby. Of course, Grandma isn't much of a status symbol (and of course, neither is the baby), but the stroller certainly is.
Moreover, in this increasingly materialistic culture, the stroller/bucket/car seat/purchase carrier prevents you from actually having to touch or interact with your baby. For some women, this is a serious advantage. (DISCLAIMER: OBVIOUSLY NOT ALL.) Also, just as slings and wraps make breastfeeding easier, the stroller makes it significantly harder -- which again, for some women, is a definite advantage. That way, if you bottle-feed, you also get to...you guessed it again...buy more stuff.
I think the women that I tend to feel the greatest amount of genuine sympathy for are the ones who, imitating this type of woman, make themselves economically and emotionally miserable and do so without really knowing that there's another choice than to follow in the touch-me-not-I'm-buying-things mommy culture that exists in this country.
Okay, </cynical rant>. Thanks for listening.