Because it will take forever and a day to charge. Actually, even if it’s a legit charger that properly fast charges according to USB rules, it may not work.
iPhone 9 fast charging power adapter revealed in pictures
It’s as fast as the rumors have envisioned and their shape looks just as rounded, too. And for many iPhone owners, charging isn’t the best as it can be.
Sony’s new USB-C headphone dongle (with extra charge port) provides bare convenience
Sure, you can listen to music with a standard pair of cans AND charge your phone at the same time, but you can’t charge it quickly nor transfer data to your phone.