I don't think companies think causalised voiceovers are what people relate to, just that people have moved on from received pronunciation... it was the jolly old whipper snapper voiceovers that didn't help viewers relate anymore. Peter Dickson has proved that with his exaggeration for E4.
Thing is though, where were the "old-school" announcers with RP anyway?
Putting aside YTV for a sec, as they persevered with RP annos for a very long time after others had slowly retired them (and I mean no disrespect to Maggie Mash, John Crosse et al as they were fine artists), most other stations' announcers weren't RP at all.
This was nothing new. A whole slew of announcers that I would trace back to the ABC style of the 1960s were still current, and not sounding in the least bit old fashioned well into the 1990s. Think Bill Steel, Tom Edwards and Peter Marshall. Some others, like Kathy Secker had had regional accents years before it apparently became trendy. Neville Wanless, a man with a strong Durham accent off-camera and a distinct lilt on-screen, had joined ITV in 1967. George Taylor of course had started all this off in 1959, and he did do some announcement work in the early days with a fairly heavy Geordie accent (much more natural and pleasant-sounding than Marcus Bentley's forced Teesside drawl that's for sure).
I don't really care about accents as long as the announcer sounds enthused about his work, and speaks with reasonable clarity. When the remaining regional announcers at STV and particularly UTV are caning the main station with all the money, you know something is wrong.