Power drain, burner inserters, reflections and some

[EstebanLB]

I'm gonna start with a question: Why do burner inserters don't have power drain? Or in this case "fuel burning drain". Is it because they work on burning fuel? or is it becasue they are from the burning fuel tier? Why do the electric furnaces have power drain but the others don't?
Why does power drain exists at all? If power drains is explained as some sort of sensor machinery that needs electricity, how does a burner inserter knows when to pick something up?
Is it this way for gameplay reasons?
Please don't kill me for making this questions, but I'm really looking for an answer that lets me sleep

[dognosh]

Why don't belts require power ?
It's a gameplay decision at a guess

[TruePikachu]

For the inserters, the electricity probably goes towards speeding up the possible reaction time, from what the internal miniture power source (the same thing that powers belts and offshore pumps) can provide.

For the furnaces, it might be a side-effect of allowing the use of modules, since the furnace needs to look for any nearby beacons as well.