"To me it feels like wearing a seat belt."

It does to me as well - the difference being that I don't feel comfortable in a car if I haven't got a seat-belt on. And I don't feel comfortable without a strap, even when I'm sitting down playing my guitar, which I do a lot more often than I play standing up.

Some instruments, like the bouzouki, are really tricky to play without a strap, I've found. Especially if you ever play the bowl-backed Greek type, or the Italian type mandolin, which is also bowl backed.

When I've played the banjo I've felt the same - it's not a question of stopping it falling down, because I'm sitting anyway, but rather that wity a strap taking the weigt on my shoulders the instrument feels more part of my body, rather than just sitting on top of me. I imagine it might be a bit like the difference between playing a keyboard like a piano, and playing one on an accordian attached to you by harness.

Also there are occasions when it's convenent to be standing up when you're playing, and I can't see then how you'd manage with a banjo without a strap. They tend to be heavy buggers. I've managed to play a guitar standing without a strap, though it cramps the style - but never a banjo. So even if you continue to prefer to play without the strap, it might be worth practising a bit with it in case that situation arises.

Have you experimented with fixing the strap a different way? I know some people find anchoring the left end to the machine-head-end is better for them, though I've always found fixing it on to the body of the intrument, or the top-end of the neck is better for me.

But it's whatever suits you best that's best for you. The old-time banjo players weren't using a strap or not using a strap because that was the right way to do it - they'd have done what was most convenient. Likely enough they'd have used a bit of rope instead of a strap anyway, I'd imagine, since it's cheaper.