I can see where you're coming from John, but I think it ends up coming down to a po-tah-toe versus po-tay-toe kind of discussion.
If I create a protile, add no sources, and move on with the expectation that someone else will add them later - I get that. It could be literally impossible to determine how they established their facts, and should be corrected as soon as possible.
However, if I create a profile, the bio reads essentially "Born, Died, Buried" and there are numerous sources laid out in chronological order directly below outlining their life, then I put that in a stage 2 sort of place - where the profile is in a usuable format, others can interpret as they may or even correct my facts if they feel I've erred, but it doesn't mean that I'm done - just that I can feel comfortable moving to the next unsourced profile to get it to this stage as well.
And then, as you mention, there's further work to be done in a full bio, with references, and honestly there's been very few that I've been able to get to that point where I've felt I had the facts in a usable format where I could begin adding reference tags. That last part just plain takes time for me, and in most cases, I just haven't got around to it.
Could I? Yes - however, when I first started here, that was too technically challenging. The references tag was something not explained well as far as I could tell, and so I created numerous profiles up front without even realizing its purpose. Once I understood, there were far too many profiles now under my watchlist to simply go back and completely rewrite them all from scratch. Plus, in my writing style, the footnotes have always been the finishing touches on any paper I've written, and so very few of my profiles have reached the final draft stage where they would receive those.
I see your point that if I were focused on a single profile at a time, editing from start to finish to make that profile to its final draft stage, I would naturally put in ref tags as they would then fit into a more robust bio, but I'm facing too many challenges of just getting my profiles into usable order and my time is better spent ensuring I have an adequate source pool to work from for now, and I'll write and ref the bio at a later time.