It took me a while to understand this also especially in the US where everyone complain all the time they work 80 hours a week, especially in tech. In my experience, only a very small fraction of those claiming to do >45hours a week are actually working that much.
I think for a lot it provides them a subconscious feeling of importance, and/or an excuse for failed goals in their personal life.
The trouble with programming is it is virtually impossible to measure. If I employ a brick layer I can count how many bricks they lay and whether the wall is straight.
Management in our industry doesn't have this luxury and programmers realise it. The inevitable result is people start to measure how long your seat is kept warm and use that as a poor proxy for productivity. You also start to see politics seeping into everything.
If you are lucky with your employer you might be able to avoid it but I think that is unusual.
I can personally speak to this because during the times I was working long hours, I was avoiding some other aspects of a personal life and was using programming/work as an escape. This paints some of my perspective on seeing coworkers who are working these types of hours. I am unsure whether they are passionate or are avoiding other things.
I think for a lot it provides them a subconscious feeling of importance, and/or an excuse for failed goals in their personal life.