Large cascades are rare like the one in Ohio a few years ago, System operators do an excellent job for the most part, but trips due to transients are common, system configuration. I have lost units because of very strange system happenings such as a guy who tried to make love to a 345 KV line in a switch yard.
The trade off is a huge intertwined grid that would handle loads faster but that would be very expensive and would string power-lines in places people would not want. The trade off is the occasional cascade and ignorant people seeing black helicopters.
In the Navy I was an IC-man on one of the first 1200lb steam systems. It took the EMs a bit of work to get it dialed in. And this was a micro grid compared to what the power companies run these days.