My daughter's analysis (DePaul student living in Chicago Lincoln Park area) is that the Chicago Divvy Bike program is way more convenient for her than having her own bike. She does have her own bike (cheap SS) which she still rides to/from work. But when she wants to meet up with friends or go to events or places around town, she says having to figure out what to do with her own bike is a big hassle. Friends meet up and take public trans to some place else. With the bike share program she grabs a bike and drops it off near her destination. No worries about where her bike stays and how to get back to it.
I hadn't thought about it that way.