Now there I do agree with you. Having technicians on site is a good thing as it is probably cheaper to pay to employ them than to continually compensate pax/airline for missed flights. Although unless you have one technician for each lift (which would definitely not be financially advantageous) you do risk having a problem with summoning people from far away or having two breakdowns at once - but even then you're still better of than if you had no on-site support at all.