It's hidden in the sense that the normal user does not see the true cost on their energy bill. You perform a search and get the result in milliseconds. That makes it easy to get the false impression that it's just a minor operation. It's not like driving a car and watching the the fuel gauge and see the consumption.

Of course one can research how much energy Google consumes and find out the background – IF you're interested. But most people just use tech and do not question or even understand.