Why Ashtrays on Airplanes?

The United States Federal Aviation Administration said the “requirement for the presence of an ashtray on or near the lavatory door provides a convenient disposal location for cigarettes (or other smoking material) and thereby ensures that there is a place to dispose of such material in the event that the 'no smoking' ...

Why do they still put ashtrays in airplanes?

So why do aircraft still have ashtrays? The answer is because people will and do still ignore the rules. And so, just in case passengers are absent-minded and place an aircraft's safety in danger by smoking in the lavatories, it remains a Federal Aviation Administration (FAA) requirement to have an ashtray.

When did they stop putting ashtrays in airplanes?

US airlines started banning it in the mid-1980s, and it was banned on all domestic flights in 1987. It is only since 2000 though that it has been banned internationally (this was when the FAA banned all airlines from entering the US if they permitted smoking).