Because they don't want to be involved in operations in Russia, especially while having Ukranian employees. As the GGP points out, any transaction in Russia implicitly helps the government through taxes.

They have put their morality and employees' above whatever business they got out of being in Russia.

Once upon a time trading with the enemy would get you shot. Now obviously those days are past and it is no apparently perfectly acceptable to do this (see: German Gas), but for Namecheap this isn't about money, but about the fact that their employees are mostly in Ukraine and that you are effectively asking them to continue to trade with the party that has declared themselves their enemy, which they - in good conscience - probably can not do, effectively or at all.

If your country was invading mine and while I'm trying to stay alive and keep those near me safe, food is running out and worse would be aware that my employer is still serving customers on the other side of the divide I would seriously consider giving them a piece of my mind.