Given today's current stringent emphasis on fuel economy, it will happen daily if the weather is bad.

It costs gas to carry extra gas to the fligt levels, so airlines don't want us to tanker any more fuel than necessary. Reduced fuel loads usually work in nice Wx, but in marginal Wx they often give us the minimum to shoot an approach, miss, and go to the alternate. This means that if you get a hold at the planned destination, you will likely have to divert immediately...if everybody diverts, now you have a stack to get into the alternate. That's where it can get scary if you didn't take a few hundred bonus pounds.