One advantage of letting weeds grow for weeks is that they are very easy to see, and each weed takes up so much space, a bit of pulling opens the garden up amazingly fast.
And then there are the Hollyhocks. I had three clumps that produced beautiful flowers last year. As they are biannual, they are gone. But they left their children - and oh, they were prolific! If I leave them be, next year I will have a garden that is a single mass of hollyhocks. Hmmm.... it might be interesting.