Back in a previous life it was standard procedure after take off to apply the brakes before the landging gear was retracted, the aircraft a Macchi MB326 jet trainer.
On the Boeings I have flown the brakes are automatically applied when the gear is retracted and if you have a brake capped due to a malfunction then there is a time limit after takeoff before the gear can be retracted.
Main gear liftoff speed, in a max weight aeroplane, is around 170kts/310kph so the gyroscopic effect would be considerable if the wheels were not braked.
Regards,
BH