When I was a kid I had a '53 Pontiac that of course had practically nothing in the way of passenger safety, including a single brake-line system.
The car had been hit in the left rear fender and had been fixed just before I bought it.
One evening as I approached a red light the brake pedal sank to the floor. I coasted across eight lanes of traffic before the thing would stop with the "emergency" brake, but with, amazingly, no two objects occupying the same space. The body shop had fixed the fender, but unnoticed was the brake line that had been pinched and had split.
Being an ignorant kid I knew nothing about checking brake fluid, but even if I had, being immortal, I probably wouldn't have checked it anyway, because the master brake cylinder was under the floor, whereas the radio wasn't so it was fixed first.
The mechanic at the Esso where I had the brake line fixed explained about brake fluid and its habit of attracting water and boiling, causing bubbles and sailing across eight lanes of traffic, or worse.
Any used car I bought after that always had its brakes bled, just as it always had an oil change. I get new fluid every three years. I won't even unscrew the lid of the now-visible master-cylinder. (I would if the thing was really low.) My car's due now. The problem, though, is finding a shop that would let me watch to see if the job is thorough and making sure the mechanic isn't using fluid from a previously opened bottle.
I'd do it myself, but thereby lies ruin and death. I'm a klutz of the first water. But I suppose that helps the economy.