The purpose of sanctions is to increase friction and make the targeted entity less competitive. Nobody expects that they work perfectly, because there are alway

The purpose of sanctions is to increase friction and make the targeted entity less competitive. Nobody expects that they work perfectly, because there are always strong incentives for bypassing them. But the effects are often very significant in the long term. For example, see the differences between South Korea and North Korea. Nobody actually wants Russia to stop exporting oil, because they are one of the biggest exporters in the world. World economy would take a huge hit if that much oil disappeared from the market. The purpose of the sanctions is not to prevent Russia from exporting oil, but to reduce the amount of money they get from selling it.