Short battery life
Its like owning a car that will always run out of fuel when you're on a long trip. The indicator showed the tank was full, until it went right down to zero in less than a kilometer.
Its like watching a good movie on TV and halfway through the movie you get a warning: "This movie will end abruptly after a few more warnings".
Battery life can stay in waiting for days on end, and then dissappear in a puff of smoke the moment you touch the device.
Never trust those battery life indicators. They can be easily manipulated with just a few minutes worth of charging.
What I've never quite understood, is what makes modern, techy battery life so mean and quirky, when compared to traditional battery life. No-one complained about a radio's battery life. The whole thing became an issue around the time mobile phones started appearing in Europe. Or 15 years later, if you live in the US.