Youtube is full of examples pilots landing gear up, with the gear-up warning system clearly blaring in the background.

https://youtu.be/5McECUtM8fw?si=DwasT3T_9vHxLczn

This does not only happen to little propeller airplanes. Heres an Airbus A320 where the pilot managed to land gear up despite the presence of all kinds of safeguards and automation.

https://www.flightglobal.com/safety/pia-a320-crews-fatal-lan...

Humans are funny animals.