• It is in the interest of most Western countries to preserve/restore the territorial integrity of Ukraine. This is part of their interest to preserve the established international order, which benefits them.
• It is not in the interest of most Western countries to have the war escalate to other countries, eapecially not other EU or NATO countries.
• Russia has threatened to escalate the war if things don't go as Russia wants. It is probably not in Russia's interest to start another war while they are not winning the current one, but the West might be reluctant to bet too much that Russia sees the Russian interest the same way.

Net result, Ukraine is getting considerably more aid and weapons than other countries in similar positions, but less aid and weapons than Ukraine might wish.

• It is in the interest of most Western countries to preserve/restore the territorial integrity of Ukraine. This is part of their interest to preserve the established international order, which benefits them.
• It is not in the interest of most Western countries to have the war escalate to other countries, especially not other EU or NATO countries.
• Russia has threatened to escalate the war if things don't go as Russia wants. It is probably not in Russia's interest to start another war while they are not winning the current one, but the West might be reluctant to bet too much that Russia sees the Russian interest the same way.

Net result, Ukraine is getting considerably more aid and weapons than other countries in similar positions, but less aid and weapons than Ukraine might wish.