Flights Deals From Dallas To Branson

I have an airline approved collapsible footrest that I have used for three years. I fly approximately 30 times a year. The flight attendant had me put it under the empty seat two seats in front of me during take-off. I've never been asked to do that. I was able to retrieve it but by that time we were putting up our tray tables and I was asked to put it back under the empty seat or put it in my backpack. I never got to use it a single minute of the flight. Is this a new rule? Or have the hundreds of flight attendants in the past been breaking the rules by letting me use it during all phases of flight?