Because they love to complain, loudly! I mean, Leo is the sign that has the most biggest personalities in the entire zodiac. They cry louder than other signs, they laugh louder than other signs, etc. They love to scream at others for their mistakes and never realize what they've done wrong. They complain against everyone because they must feel good about themselves. Remember, fire signs are the most arrogant signs out of all elements in the zodiac. Unlike earth signs, fire signs don't see the good traits of other people. They love to spend money on expensive items in order to look good and stylish in themselves. They can be extremely aggressive, especially Aries. They love to fight and yell with just everyone around them. Haven't you ever heard that Sagittarius is the best sign at playing sports? I mean, just take a look at the famous sport players, most of them are fire signs, and most of them are Sagittarians, the rest of them are Arians and Leos. They must release their strong energies into something they have to do every single day in their routines. But sometimes Leo can be good. I mean, they can be very protective of their loved ones. They love to protect Libras since Leo supports Libra.