How many people use it for payments is not the right metric, it’s not the payments that cost a lot of electricity it’s the competition to win block rewards where more energy means a higher chance of mining a block.

Indirectly, if a lot of people use it for payments it may be worth more and attract more mining competition.

Bitcoin and most(all?) crypto currencies pretty much suck for payments. I think a BTC transaction costs around $16 USD just to get it on the blockchain now. Plus transactions are not private, and they are permanently public, so even if your BTC Address is unknown today, doesn't mean it won't be known tomorrow.

There are perhaps, some reasonable arguments for using crypto-currencies, but buying groceries is not on the list. Buying Houses... *MAYBE*, since that information is already public anyway.