The subway system is a mess right now. If you look at the NYT, Village Voice, etc. you'll see a lot of misery surrounding the MTA at the moment. Wanna go to a different borough on the weekend? Too bad the 1, 2, 3, A, C, E, 4, 5, 6, M, F, D, B, N, Q, W, R, J, Z all have planned service changes. The L Train is going down in 2019 so that'll be another issue to deal with. Personally I like driving, so that was hard to give up. I didn't always feel like being squished against a bunch of sweaty bodies, watching someone try and clean up vomit on the seat during my morning commute, or deal with changing bus schedules/routes. It also can take forever to get around the city, despite all being within a few miles.
The cost of living is so expensive. Rent is outrageous, even in the "affordable" areas. My friend lives in a crime-filled area of Brooklyn and is still paying $825/month for her room (she has a roommate). Groceries are expensive and a pain to get home (I could only bring home what I could carry). Restaurants/bars are generally expensive (although I found my cheap go-to's). I love having a washer/dryer in my home, but at least I had the luxury of having a laundry room in my building (many have to drag their laundry to a laundromat). I wouldn't want to live in a walk-up building.