UV, It's a cold and damp winter morning. The aircraft hasn't flown in five days and is stored outside. The battery isn't 100%, the oil is thick and the starter old. Also the apron is completely empty.
What do you do?
1. Turn on all the lights, strobes and everything during a thorough walkaround, and turn on every possible electricity consumer while chatting with ATC about your startup clearance, departure route, squawk and the weather. Likewise during the start of the engine.
2. Only turn on the essential lights, check them quickly then shut off before doing the rest of the walkround. To request startup you only turn on the avionics that you need (one radio) and while starting, all other electricity consumers, including alternator field, avionics and lights are kept off.
1. might be the legally correct answer, but may also result in you not flying today because you drained the battery. So I choose 2.
Heck, if I really suspect a tricky situation wrt. the battery, I'm not going to check my lights during the walkaround (I can see most of them from the cockpit anyway) and will start the engine without requesting startup first. You will feel a bit silly asking for startup permission when the engine is already running but that will wear off after a while. And ATC knows how the game is played anyway.