Photo by Sava Bobov / Unsplash
Simple courtesy goes a long way.
And in certain industries (eg law) or cities (eg Hong Kong) where everyone knows everyone else, it pays extra to be courteous as you never know how the tables will flip a few years down the line. The job candidate you ghosted might later be the one in a position to say yes or no to your job candidacy when you're looking for something new.
At the very least, you might end up working in the same (or adjacent) departments. It's a small world. I remember several years ago in the check-in line at Incheon airport (near Seoul) I bumped into two guys I knew within the span of 15 minutes. One was someone whose wife had invited us to dinner at their place in Hong Kong the week before and another was someone I had met about 6 months before in Singapore. And all 3 of us in Korea on that same November afternoon transiting to different parts of the world from the same airport. Again, it's a small world.