cuz folks are enamored with living downtown. I don't see the advantages personally. the cost of housing is ridiculously high for what you get. when you live in a high rise going up and down the elevators is a pain int he ass. especially if you have a pet. and if you have kids, they can't really play outside. and if you wanna have a car down there.......shiiiitttt, ur gonna get raped. I hate places where it's a pain in the ass to have your friends and family come visit because of the lack of parking as well.
I have seen so many folks in high rises with their pets with shytty looks on their faces since they gotta take them out in the winter and walk them around the cold ass city. meanwhile I just open my back door and let my dogs out, and call them back in when I want them to come in the house with minimal hassle.
I love living in a city, but I don't really like downtown. it's not for me.
It really comes down to preference. The things that you may value when you consider a home is not the things that someone else would. Also, your priorities will not be another person's priorities and therefore the sacrifices are different. The comfort of convenience is much to be desired for alot of people downtown. Something as simple as "the view" makes a difference to certain people depending on where they are. Sometimes you may want to feel something very specific to city you live in, something unique to whatever the experience they are looking for is. You touched on that in regards to younger people who prob grew up outside the DT area and have some success and want to grant them that lifestyle, transplants who likely moved to the city and want to be right in the thick of it as opposed to being in outlying neighborhoods that may not be any different from the neighborhood in the city they just moved from, or older more established people who either already lived elsewhere and want the convenience/comfort of being "right there" or because they can simply afford to. Again this all comes down to where your priorities are in life, as well as where you are at the time of being able to afford it. Most people who live downtown, work downtown. The convenience of not needing to commute or even use CTA to have all your needs met is very alluring. On top of everything being right there near you, depending on where it is you go. Not to say you cant have that in other neighborhoods, it just depends on you personally. Where I lived, there is a 3 story Walgreens damn near connected to my building, Mag Mile and all the shopping, restaurants and bars just downstairs, view of Chicago skyline from my place in front of me, the Riverwalk just below me, the view of the lake to the left and Navy Pier fireworks going off every Wed and Sat night from my bed or living room.
I also moved because I cared less and less about the things that made me want to be down there. The very things you mentioned actually is why we moved It was never cost efficient and no matter where you live, theres someone asking "why would you live there? you can live here for this much less." Even where you are now, theres someone in Elgin looking at you about what you are paying for where you are exactly how you may look at someone for staying in the city. The same answer you would give them applies to those in the Loop and Mag Mile. "Where you are right now, this is what I want." I moved because I no longer cared that Hubbard and all the bars/clubs were right in front of my door, or the restaurants and being right there when I was usually chilling in the house because I had a girl. My city skyline view changed because I switched apts and all that just didnt have the same feel and no longer made it worth it to to pay the premium so we moved out by UIC. Its not the same but I save alot of money. Trying to buy another house or invest in another business.
because there's a greater potential reward with the same amount of risk.
and 
because gentrification in some of these other cities make ours look somewhat tame even tho it's not.
