They're perfectly capable of having plenty of hits. Never disputed that. Just look at BSE her top 20 (or was it close to top ten?) on US iTunes. Sold well enough.
Yeah. But in terms of longevity, radio airplay is needed; just look at the biggest artists from last decade like Britney, Xtina, Kelly, Beyonce. The reason they have lasted this long and are so well known is because they had hits on radio that resonates with the GP.
The boys are doing fine right now but it'll have to change down the road. The management just needs to help push their singles to radio and promote them properly.