Many mobile phone manufacturers did the same at some point. Sony used to cell phones with their own propietary sound output and their propietary memory sticks. LG did the same for sound. Then the industry matured with standarized chargers, memory and sound output. But Apple somehow got their own way, sound is just one more thing.
Few years down the line and Samsung says "I'm not signing this year, because Apple doesn't play ball and use their own cable", and the EU moved on their threat and started process on a law. Don't know if it's finally passed or not.
(the EU original intent was to limit waste, and was triggered by seemingly every single Nokia phone needing its own specific charger)