Putin has threatened so called unfriendly states to pay in rubles or have its gas supply shut off. It has said it doesn't buy things for free and so isn't going to charitable with its energy.
Europe has kicked against this with Germany saying its being blackmailed by this move. What other choice does Europe has with Russia alone selling about 40% of energy to the world.
Okay, let's say, Germany, Russia's biggest gas importer is not going to pay in Roubles and other European countries follow the step, then what? Where the fuck are they going to sell their gas and how the fuck are they going to profit? They need money to live. Also, every single day, the war requires a lot of money. Robert Habeck recently said that Germans should reduce demand on Russian gas as much as possible. He suggests Germans to lower the room temperature by one or more degrees, work remotely if possible and move on public transport.