Can't speak for most firms, but I interned at Jane Street and this definitely wasn't the case: almost everyone there worked 45 hours/week with a consistent schedule (market hours + a small buffer).
It makes sense: they value people doing high-quality work and avoiding mistakes. Everybody there was also clearly very productive—it was one of my first experiences that convinced me that long hours are actively counterproductive.
I understand other firms in the space (like Citadel) have pretty different cultures, so it's not going to be true for the entire field.
These were startups who were not making up for the long hours with financial compensation. They just felt that they were entitled to cheap labor that doesn't value their time.
Attention any quant firms-- I'll do it for 250k, 80 hours a week, 24/7 on call, fire me if I don't deliver satisfactory results.
10 years of experience in Cpp, Java, Javascript, Python, SQL, the last 5 of which as a lead (aka designing the data model and optimizing slow parts of the code base through better ds and algo implementations).
Only catch is I won't show up physically in NY or Philly or Chicago, etc.
Quant finance companies expect employees to work 60-80 hours per week.
But then again, they pay 400-500K USD to 22 year old new grads.