Even if it was fully green, you can’t run an electrolysis system from home. So you have to buy it, so there’s a market and an expensive solution.

Electricity comes out the wall.

What do you mean?

You can run electrolysis from a cup.

I know, I have one of those weird H shaped flasks with the plat electrodes.

I also have a gas bbq, yet couldn't fill up a LNG car at my house. Maybe there's something more to it than just making small amounts of room temperature / pressure H2.