You do not sound very experienced, perhaps you should go down and do a pre-flight walkround, if you are allowed, and have your Captain turn the lights on while you are there. You would then get the message. You complain of ramp trucks, with a 100watt light blinding you, so go back to your company manuals, or ask a mechanic, how many watts your lights produce?
That would give you the answer.
The beacon is on to show that the engines are running or are about to start, the taxi lights are used to show that you are under way and all the lights are used to show that you are on the runway and rolling. It is an ICAO recomendation. And of course you turn the taxi lights off just as you do the final turn onto your stand as a courtesy to the marshallers etc.