As this thread was started referring to Edinburgh departures, and this applies equally to all aircraft arriving on a Scottish control frequency that HAVE NOT been transferred from either London or Manchester Control.
It is a REQUIREMENT as stated in the ScATCC MATS Part 2 that all aircraft are identified by requesting the aircraft to "squawk XXXX and IDENT".
This is required whether or not the aircraft has been worked by another SSR equipped unit, with the exceptions as mentioned above.
So, to answer Hufty's original question, yes it is a pain, and please wait until we ask you.
As was mentioned elsewhere, this also happens regularly with Belfast TMA departures that have worked Aldegrove radar, so they get to press the IDENT button twice !
As an aside, the lack of a level report (and SID if appropriate) on first contact is also annoying, as we are required to check that as well.