Because Ukraine needs Europe's help to defend itself. And cutting gas off from Europe, hurts Europe as much as it hurts Russia.
Yep.
Don't lose track of hos much this **** is going to hurt US. When all those eurowankers start starving, Breadline Joe is gonna insist that we share our food and supplies with them, and that means AFTER demopoops and deep-staters blow-up/burn-down 30 some major food distribution and processing centers and shut down all rail traffic for shipping fertilizers just as spring planting season starts... It's as if the dufe was channeling Joe Stalin to ask about starting famines...
Europe is not paying its fair share of Ukrainian needs. Halting gas transit is a mean, but good way to get EU to pony up. I believe that a few have decided to go into debt for those “needs”.