We kept nagging at the boys to shower daily, because the locker room stench was killing us. Finally, I decided to try another brand of deodorant (Arm & Hammer). Problem solved! It seemed the gel on the other brand was so sticky, it never washed completely away, trapping odors. I told my kids to throw the old brand away, pleased we'd figured out the problem.
Youngest son: Okay. I've had that one for a couple of years anyway.
I did a double take. "How do you have deodorant left over for two years?
Youngest: "I didn't like the smell, so I usually didn't wear it, but don't worry, I like the new stuff."
Never assume that you know what makes your kids tick. Unlike a video game, there is no "expert" parenting level.