There are more aircraft based there, than you seem to know about.
True. In addition to the Tutors there are four light civil aircraft. None of them fly at night either. Justification for a permanent H24 full radar service?
Just the other day two Lossie Typhoons did a weather divert at night. Where did they go? Liverpool. Because Leuchars minima for runway 08 are significantly worse than Lossiemouth's for runways 05 or 10 - and significantly worse than pretty much anywhere with an ILS.