1) Basically all of western Europe is in NATO, meaning none of the countries there neighbour any potential aggressor. Russia would first need to barrel through Poland in order to get to Germany and France, for example.
2) Most of european militaries are a complete joke that wouldn't even slow down the enemy.
3) All of them count on US to do the fighting.
4) Despite the sad state of the military, it still manages to eat up massive amounts of money every year as well as features one of the most corrupt sectors in almost any country.
With these facts in mind, is there even a point for a western European country to have any army whatsoever? Their armies are incapable of doing anything useful (except maybe pretending they're doing something in Afghanistan and syria so that the US can pretend it's not there alone), they are irrelevant when it comes to combatting foreign aggression, they are not threatened by any of its neighbours and they have the US to do any fighting for them should Russia try getting there through Poland. So why not ditch the army entirely? Just dissolve all of it and use the money more constructively, send all the troops into the private sector to fuel the economy, and sell all the left over hardware for a quick buck.
Alternatively, they could increase military spending to actually make their army useful for something, at which point it might be worth keeping, but they don't seem too keen on doing that.