I think young children (under about 3) have a hard time comprehending the word "don't", which is a lot different than "No".
My twin sons were about 2-1/2. We were visiting my parents, and the boys were "helping" my mom plant flowers in the garden. When she encountered earthworms, she gave them to the boys to play with - a new expereice for them.
First Bryan came into the kitchen, showing off his worm: "Grandpa! My got a worm!". My Dad made a big fuss: "Bryan, what a nice worm! That's really cool!", but ended with a stern look and "Don't eat the worm!" We could see Bryan's thought process on his face - a look of disgust (it had never occured to him to eat the worm), then thoughtfulness as the wheels turned in his head "... eat the worm... Grandpa said eat the worm...", and he went back outside.
Moments later we had an instant replay of the entire scene with James (gotta love twins!). He got the same look on his face, and we could see the wheels turning the same way.
A few minutes later heard my mom laughing in the garden. Both boys had dirt on their faces; she had just seen James spit the worm out of his mouth. When asked where his worm was, Bryan proudly replied "My ate it!"
I'm convinced that the word "don't" went in one ear and out the other - not because he was willfully disobedient, or even because he didn't understand what it meant, but because the words that followed had a bigger impact.
Eliminating "don't" statements takes some effort, but it really does work, especially when they are younger. Imagine if I told you "Don't think about a chimpanzee wearing a red hat, riding a tricycle". That image is going to come to your mind, and you will have to consciously think about something else to get that image out of your head. When a young child hears "Don't jump on the bed", even if they have the impulse control to stop, it can be pretty hard to think of an alternative, when the last thing you heard was "jump on the bed!"
"Just to look at" and "sit on your bottom" and "gently touch" are all "do" statements, which puts the onus on the adult, not the child, to think of an appropriate action. When the child sits, then the adult can say "Climbing on chairs is dangerous - you could fall and get hurt". It also give us the opportunity to say "Thank you for sitting on the chair!" or something to reinforce the behavior and habit you are trying to develop. With a little effort, it becomes second nature to tell them what to do, instead of what not to do.