Why driverside headlight is brighter than passangerside headlight

Recently just after the car health check, I found the driverside headlight is brighter than the passengerside one. (the report saying it is normal, and the check including the headlamp alignment, maybe that why it looks differently now after correct adjusting by them?)

I did a quick check online and found people saying this is normal since the driverside headlamp is adjusted to a different level/angle compare to passengerside and that why it looks different brightness between the twos. But some claims that the passengerside should be brighter than driverside since you don't want to blind the opposite driver. Others say they should be same brightness.

So I am wondering why there is difference between the lights, is that a trick played by free car check and 'asking' you come back for a paid check and even a new pair of bulb...:(