Think of all the bands you know who have a singer. Now narrow it down to a singer who is also an instrumentalist… and playing that instrument most or all of the time. Unless you have very odd musical tastes, you probably started with a large number (be honest, you gave up counting after you ran out of fingers and toes….) and got down to a smaller number. You might still run out of fingers and toes though. Now refine it further – how many bands do you know where most of the main singing duties are held by the person who is also playing the bass? With the people I know, some will still be able to get to double digits or beyond but it is likely to be a tiny subset of the potential original list.
Within one of my main musical activities, leading Christian worship music in church, the subset is even smaller. It isn’t unknown but, although I know plenty of bassists and plenty of worship leaders, I know fewer bassists who regularly lead worship and fewer still who regularly lead on bass.
I’ve got a theory on that. It isn’t that bass is unsuitable for the task nor that it’s a lot harder than, say, guitar. I think the main issue is that we don’t hear it much and so, even when people think about it, they don’t have examples to follow. Maybe it by virtue of being a better player or more open tastes – or just being older and kind of gnarly looking – but I don’t often get people telling me how to play the bass anymore. Anyway, even if I’m swimming in a very small pool, I’ll keep on setting an example.