After 80 years of US largesse? Methinks others are late.
Think about this...at NATO's 1947 formation, with the Treaty of Dunkirk, the signatories were the UK, and France. In 1948, the Brussels Treaty added Belgium, the Netherlands, and Luxembourg. We, Canada, Italy, Portugal, Iceland, Norway, and Denmark joined in 1949.
Of this group, all but us, Canada, Iceland, and Portugal were still in ruins since after V-E Day (you may recall the Marshall Plan to help rebuild and stop starvation). For Heaven's sake, it took the UK until 2006 to pay off their WWII debt to us. Especially through the first two post-war decades, no other countries had anything like our capacity for defense. So; as Western Europe gained strength through the 70s and 80s, their contributions grew, as did NATO in the face of the Soviet threat.
Then the Soviet Union collapsed, ecpnomically and financially. Germany reunited, and the EU developed in a relatively threat-free environment. Only when South Ossetia happened did NATO begin to redefine itself, after 25 years, as again defensive with one major threat.
It's not so simple as 'we always paid because NATO wouldn't;' for decades, they couldn't, then for decades, there wasn't much threat.
Since February it's been different. Good. Better late than never.