A big part of spend money represents used energy - mining of resources, refining those resources, making whatever thing I am buying etc. And a lot of things we spend money (and energy) are not strictly necessary. However, there are probably some things that you approve of and consider to be OK, but not others.
Let's say I installed solar panels on my house and now have "free" power when the sun is shining. Am I allowed to use it however I want, say, by running an inefficient light bulb or some other device that does not have the best efficiency?
You could say that if I did not use the energy, then, assuming my solar power is connected to the grid, others could use it, but at the same time, if I was not planning on using it I would not have installed (as many) panels.
If I said that I have a good gaming PC that uses, say, 500W and use it to play games 4 hours per day (using 2kWh per day on games), would you approve of it? But what if I do not have a gaming PC and instead use the same 2kWh on incandescent lightbulbs or a vacuum tube radio? Would you disapprove now even if it is the same amount of energy used "for fun"?
Similar with a car? It uses however much fuel it uses, but should I have to submit a trip plan to the government for approval? After all, I may be just going for a drive or going to some place where I do not strictly need to. Should I be able to get an exception based on the low total amount of kilometers traveled and fuel burned?