1. They understand the day to day Operations of the company better.
2. Non-IT people find it easier to deal with them.
3. They're easy going, less demanding in terms of the Company culture and technologies used.
4. They tend to stay for long time in the company - that means Loyalty. Most companies appreciate and reward Loyalty.
5. They aren't Incompetent. They are just good at what they do, for long time, which new comers might dispute as being lazy, not passionate about technology.
Lastly, most of the jobs don't require you to be genius.