The problem is, many of us hinder innovation with constraints, rules, and overall, realism. If you always take the approach that creativity will ultimately lead to a unfinished or unwanted product or service that ultimately doesn't amount to much, then you're no different than the hypochondriac who won't leave the house in fear of catching a disease. 

I actually wrote an article talking about just that for this site, but have never submitted it. I too feel that a lot of the realism hinders great ideas that lead companies to great success. That's because like myself, so many of us are caught on all the critical details of an idea. Like if it can scale, if it's secure, how much money will it cost, what technologies will we use, and so forth and so forth. Eventually, you're just finding ways to dismiss something rather than create something.

The idea that creativity is going to ignore all rules and dwindle into a waste of time is a sign that you really don't have much faith in your team. Many of the creatives I've worked with over the years are fully understanding of the game and do not go off that beaten path. They are thinking about what is possible and not possible, but not thinking about all the obstacles in their way because ultimately, no one will come out there house nor take risks if the analyze something down to the grain.

It's a balance and good creative people wield that balance like a double-edge sword. Bad ones end up stabbing themselves in the foot and costing the company thousands if not millions of dollars in wasted time and effort.