Why is it important to have resistance in the floor when teaching ballet? is it to promote stretch and strength?

One of my esteemed teachers always said, "The floor is your friend." I always related to this. What we are required to do as dancers seems superhuman at times. But, that floor is ALWAYS there! Brushing into the floor ("using the floor") executing tendus keeps the working leg straight and connected to the movement of the step. "Feeling" our supporting leg "rooted into the floor" helps the dancer to perform adagio, pirouettes, balances, etc. The floor is our "touch stone"...Think of it! During barre exercises, we hold that apparatus as a balancing help when perfecting basic technique and warming up our bodies. But, when it comes right down to it in the end, it's just the dancer and the floor!

Thankyou very much for your reply Gina. Very much appreciated.
Quick Question for You - using the resistance of the floor in an exercise for example - Tendu - would one be correct in saying that it also helps in the way one could strengthen both the feet, legs etc?

Hi...It absolutely strengthens the legs and feet working the tendu in this way. It instantly adds "quality" to the tendu when the dancer is not "coasting" on the floor trying to execute this step.