It's been legislation for a long time for Uk Licenced Engineers. Those that weren't covered were mechanics and unlicenced technicians.
There's always rogues in every community (pilots included) but the majority involved in the aircraft industry i've met are well aware of the consequences of their actions.
Don't forget the crews influence on safety for a particular aircraft lasts the length of their sector, the engineers work goes untouched for years.... Food for thought?
As a side note, i've no idea why the limits for flight crew and ground staff are different. Should be one rule for all.