Guy at the nursery in Tulsa told me to stop staking every young tree I plant

I was at a nursery off Route 66 in Tulsa last spring buying a redbud when the older guy working there said most young trees grow stronger if you let them sway in the wind instead of tying them tight. I had been staking every single tree I planted for almost 4 years, following what my old crew lead taught me, so I argued with him for a good 10 minutes. He walked me over to two maples they planted 3 years back, one staked hard and one left free, and the free one had a trunk almost twice as thick. I went home and pulled the stakes off 6 trees in my own yard that weekend, and not one has leaned over or fallen. Now I want to know, do you all stake your new plantings or leave them loose?