In case You can read German,
here is a news report on a lightning that struck a DH8D at LOWG a few years ago.
The lightning struck the aircraft, luckily with noone on the headset. Nevertheless, three loaders that were working on the aircraft and two flight attendants that happened to hang around outside had to be hospitalized with burns and injuries to the head.
Working on an apron during a thunderstorm is doubtlessly dangerous, and while they may be annoying, those security measures are in force for a good reason.