My guess is they suspend the net out of concern for the equipment. There's now two discussions going on with this thread. One is the possibility of being hit by lightning while driving a vehicle and the other has to do with the things we do to protect our radio equipment during an electrical storm.
My personal preference is to disconnect everything from the rig to isolate the rig from nasty weather. On the big towers, all transmission lines, power lines, and rotator cables are disconnected at all times with all the transmission lines dead ended in surge protectors. All of that will probably prevent lightning from damaging my equipment. It won't prevent lightning from hitting the house.
Lightning is bad news to the radio operator, especially if concerns about it aren't a part of the radio equipment installation.
1991 FJ80 converted to an HDT with an A442, Safari intercooler, 3" exhaust, factory Toyota subtank, 3" lift, 285's, Warn 9500xi, rear drawer system, 42qt Engel fridge. This rig is currently for sale