The resources are required to process transactions securely in a distributed network. You could do the same thing much more efficiently by putting all your trust in a central authority; it's called a bank. But that's not solving the same problem.

Ok, let me rephrase my prior point. If I have my PC mining and then disconnect it, does the Bitcoin network suffer in any noticeable way? If there is no noticeable benefit from my single PC then the resources being used by that PC aren't contributing to anything of value.

Yes, resources are required, but the amount of resources used far and away exceeds the amount of resources required.

> If I have my PC mining and then disconnect it, does the Bitcoin network suffer in any noticeable way?

Yes, there's a computational power threshold to perform certain attacks against the network, and removing your node marginally decreases that threshold.

Is it necessary? That depends on your priorities and your threat model.

There is a correspondence between the output and the resources consumed. If your output is negligible, then your resource usage was proportionally negligible to the end of providing the network with monetary units.

Your argument neatly cancels out your conclusion.

If you stop paying taxes in a typically sized country, the country's finances do not suffer in a noticeable way, either.

The network is made of the nodes.