It was very true to say that Radio 7 had hardly any publicity on R4, and when visiting my sister's 'holiday home' I found a bedroom TV had Freeview but one had to select an option to be able to even jump through the radio channels.
For well over 15 years, the BBC has had radio service on satellite with Sky and others and although in the early days it was only mono and 'test broadcasting' (with Radio 5 playing a loop whenever there was sport on, telling listeners they could not play it via satellite), it has been the case that in TV shops and most literature regarding Satellite or Freeview, the fact radio services are included is hardly mentioned, or definitely not given equal billing, so little wonder that the 'digital' channels have not been prominent.
R5 Sports Extra gets a lot of mention, which, considering FiveLive is on rubbishy 'AM' (Medium Wave), and the Sports Extra is on DAB / digital, means there is bound to have been interest simply to be able to hear the sound on FiveLive without the crackles and buzzes of AM...
6 Music had fewer listeners until there was the rumour of closure. 1Xtra may be popular with teens and twenties, and with sessions where 1FM and 1Xtra are linked, there must be plenty of promotion for 1Xtra, but there was hardly a mention of Radio 7, or before it was called that, BBC 7.
It was alone, playing comedy from the 50s to the 90s, and drama too, of course. In the last few years they have been funding new material exclusive to the station, mostly tied in with comedy, at Edinburgh and other events, and there were moans about the switching to childrens material from 0500-0800 (some of it had been in the afternoon and it had been running later, up to 0900, I think), but there was little or no mention of what was on BBC 7/ Radio 7, on R4, the most obvious source of listeners, even when they rebroadcast the Friday 18:30 comedy shows on R7 2 weeks later. Even Feedback, in answer to some question about lack of podcasts, didn't mention the rebroadcasts (handy if one was away on holiday for 2 weeks as it made it easy to enjoy the 'missed' items using iPlayer).
I think there are far too many promotions on R4 (2 to 4 per hour, at least most hours from 05:20 to 00:45) yet they mentioned more about what was on TV, or paying the TV Licence fee, than they did about their 'sister channel', didn't they !! Daft planning at the Beeb, for sure.