Coming out to find your brake lights still glowing - or a dead battery from them staying on - is a common and fixable problem. It almost always comes down to the pedal switch. Here is why brake lights will not turn off.
A stuck or misadjusted switch
The brake light switch is held open by the pedal at rest; if it sticks closed or is out of adjustment, the lights stay on; see brake light switch symptoms. This is the most common cause and an easy fix.
A crumbled pedal stopper
Many cars have a small rubber bumper (the stopper) on the pedal that presses the switch open. Over time it crumbles and falls out, so the pedal no longer reaches the switch and the lights stay on. A cheap replacement bumper fixes it.
Wiring or a stuck pedal
Less commonly, a shorted wire or a pedal that does not fully return (a binding pedal or floor mat interference) holds the switch closed. Check that the pedal returns all the way up freely.
What to do
Inspect the switch and the pedal stopper first - replacing one usually solves it. Do not just pull the fuse; you need working brake lights. Keep the brakes themselves fresh with quality pads and hardware.