The Reason I sing unaccompanied include the following;

I don't have to cart around heavy and cumbersome instruments in cases around festivals, which mean I can squeeze in and grab a seat in the sing around sessions.

I don't have to waste too much time doing sound checks, when I get gigs.

I don't have to tune up, though many folk do say I do sing in obscure keys.

I don't have to pay a fortune on forking out on instruments and their upkeep.

And finally it's like Martini, I can do it any time, any place, any where.