The best questions on stack exchange are well-researched, specific and detailed, but on area 51, I'm limited to 150 characters. It's hard to show off what great, well-informed questions could get asked in 150 characters, and I've had to edit down substantially.
Because example questions should be like headlines: you see a few words and you build yourself an expectation what can be the question about.
Of course it is difficult to ask question which will be understood as you wish, when you have only question headline, and not body, like on normal SE. But you have only 5 questions per proposal and you are expected to think carefully what you want to ask.
Note also that the potential follower/commiter would look on the questions and the first impression is deciding if he or she would follow it. It's hard to make good impression when question headlines would have 1000 or 2000 characters.
The example questions are just that: examples. They exist to define the scope for the site. They define what the community thinks should be on-topic for discussion, nothing more.
The example questions are there simply to start filling in the scope for the site. I.e. "What type of questions would you like to ask?"
These aren't supposed to be fully fleshed out questions with details and background. Users don't typically know enough to avoid answering these questions as it is. This would only exasperate that problem. The purposely-short title is enough to convey the type of questions you'd like to ask without drawing out trifling complaints and criticisms about the irrelevant details. We can do that on the actual site. grin
