That's not how majority attacks work. You can't steal coins by having the majority of the hashing power on a network. You could double spend, and prevent certain transactions from confirming. The obvious answer to this is it's incredibly difficult to keep such an operation ongoing, and online 24/7. Plus, at the end of the day is it really work the expense to prevent certain things from happening?

The only reason I see people attempting majority attacks on a particular coin would be if they were competitors, and they strategically attacked it at the right moment to cause doubt within it's followers. Otherwise, I don't think it's beneficial to anyone.

Having just 51% isn't really a enough either. It would be much more effective the higher percentage of hashing power you have.