Just for fun (ha..) I went on YouTube and picked a year -- 1992 -- searched for "Magic Kingdom 1992" and looked at some home movies of the crowds and pathways, just to compare the volume/amount, and sizes, of strollers in the parks, and strollers parked by rides and restaurants... it was still very very crowded, but, very very different. What's changed between then and now...? I dunno. Just an observation. I personally would have preferred the option of a more minimalistic, compact stroller when my kids were born but at the time it was difficult to even find anything I really liked. So I was happy when I was able to kick them to the curb and use the single umbrella only.
What changed since the 90s (and 80s)?
1) The middle class has more disposable income
2) There are simply tons of stroller options now (compared to the 80s/90s) -- and because of #1 - parents are willing to spend money on them.
3) Because more people are willing to spend money on them . they stroller makers make them bigger, better and "more comfortable" or convenient.
Plus:
1) More "stuff" that we feel we "need" to be comfortable - sunscreen, hats, water, snacks (and thus wanting a vehicle to tote it around).
2) The willingness to bring small children to the parks. (My parents left my younger sister home with my grandparents on my first trip in the late 70s. A few years ago, I took my 5 mo daughter (with my 4yo son) to Disney for a short 3-park day trip). We rented a double stroller for those days. And while it was convenient .. it did take up a lot of space.
Just everything in our society has gotten bigger, better and "more".
Like I said previously - in order to truly curb stroller use -- Disney will need to make it hurt in the wallet. Charge for infants. Or .. like the airlines do. Charge a "fee" per stroller you want to bring in the parks. I mean I'd be more okay with that than the parking fee to have my car sit at a resort if I knew it would help reduce congestion in the parks.
You could argue that Disney's prices ($3.50 for a bottle of water) cause people to want to bring in ice and wagons and strollers to bring that stuff in.
Imagine if Disney sold water for like $1.00? You'd see less people willing to try and "save money" by hauling all that stuff in the park.