Why smaller companies take baby steps in VoIP deployment

Many larger companies are deploying VoIP in one location at a time,maybe only one IP PBX.
They do this to assess performance before they jump into the deep end of the pool.
The Enterprise VoIP Planet article notes, though, smaller enterprises are less bound by such caution.

Why is this? less layers of approval with more nimble decision making; closer collaboration in the testing process, older communications infrastructure compared to larger as well as similarly sized rivals.