Europe needs a lot of what Russia has. Cutting themselves off hurts them more than it hurts Russia. From Ryan McMaken at mises.org:
European politicians are eager to be seen as “doing something” to oppose the Russian regime following Moscow’s invasion of Ukraine. Most European regimes have wisely concluded—Polish and Baltic recklessness notwithstanding—that provoking a military conflict with nuclear-armed Russia is not a good idea. So, “doing something” consists primarily of trying to punish Moscow by cutting Europeans off from much-needed Russian oil and gas.
The problem is this tactic doesn’t do much to deter Russia in anything other than the short term because Russian oil can turn to numerous markets outside of Europe. Most of the world, after all, has declined to participate in the US and European embargoes and trade sanctions, opting for more measured approaches instead.