Because the US is the driving force bheind this. European countries such as Germany opposed Ukraine joining NATO [1]. European opposition blunted Bush's effort to set a timetable on Ukraine and Georgia, which is how it became a noncommittal open-ended "open door" policy.

What's more, countries like Germany have deeper econmic ties to Russia because of natural gas in particular. European countries are, as a general rule, less interested in alienating and isolating Russia.

And there's really no difference between political parties in the US either. George W Bush's open door policy from 2008 has survived 3 subsequent administration from both parties.

It's US foreign policy that drove invasions of Iraq and Afghanistan, supports Saudi Arabia in Yemen and Israel in Palestine, Lebanon and Syria.

[1]: https://www.nytimes.com/2008/04/03/world/europe/03nato.html