First of all I think it is actually 4 hours delay on langhaul flights. Second, the airlines only need to provide vouchers if it does not affect the possibility to keep the new schedule or having people leave the boarding area will delay the flight even further.

So by delaying a intra-european flight by 1h45min and then continusly for 15-30 minutes they does not need to provide vouchers. Or 3h45min if it is a longhaul flight.

Finally, if they keep people onboard the aircraft no vouchers will be handed out...