The roads covered by pub runs and most utility rides have all been covered by 'significant' rides for me anyway, so adding them wouldn't make much difference.
Saying that, I've got almost nothing in North London. What I do have is either covered by rides up to Cambridge (which go East of Liverpool St) or the London Sightseer in 2007. Despite cycling to/from Paddington, Kings Cross, Marylebone, Edgware Road, etc for lots of Audaxes I've not Strava'd a single one of those rides so those tiles remain unclaimed.
Tiles within 10km or so are relatively simple to add, although yesterday's 50km bimble planned purely to cover tiles did send me down a wide variety of roads/paths/subways given that I didn't pay any attention to route planning other than 'that road goes where I want to go'. Makes a change from blatting around the park on roads I've seen hundreds of times though.