I have my own version:
When the gardener goes away the weeds have their day!
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.