I will grant you some units are the top dogs not requiring such tatics but your like's of lossie don't even entertain them.
That's perhaps the most important bit. MATZ "clearances" aren't mandatory but I would view them as good airmanship, certainly round here where the local MATZ is often full of rotary traffic on UHF which controllers will make a positive effort to move away from any civvy traffic transiting. For the record Shawbury have never turned me down and have always been accommodating - even with student RT. They do have an obsession with not converting QNH to QFE but one can always renegotiate...
They've also been quite sensible in the past - a friend on a CPL training trip got "controlled" in IMC, with a firm suggestion to help his student avoid the Tornado Diamond 9 coming the other way.....!