Interesting... Might I ask as to what sort of units are saying this to you? Is it area controllers, or approach units, or just a specific unit?
I believe the phrase is actually 'remain outside of controlled airspace' too, but that's a minor detail. I dont know of any increased requirement to say it to everyone, and I havent heard anyone say it other than when its necessary.
As for your last paragraph, I genuinely believe that ATCO's wont be replaced by computers for a very very long time, if ever. You might want to visit some units and then you will realise why, particularly if you go on a bad weather day (ie plenty of CB's, turbulence and icing). Its much more likely that pilots will be replaced completely by computers first, and I cant see that happening either even though the technology is available to do it already!
LOA
ps, you're doing exceptionally well if you've spoken to 50% of controllers, I reckon i'm only at 4% of the UK ones!