Then you misplace the lot and you're out $50-$100 worth of kit, rather than a $4 set of 3.5mm headphones, which you already have six compatible pairs of sitting in the culch drawer.
If you have a phone that doesn't come with a 3.5mm headphone jack, then you're able to spend €10 on a dongle to make your $4 set of 3.5mm headphones work. If you cannot afford that, then you have one of the many phones that do have a headphone jack. I'm sure that, if in the future everyone for some strange reason got rid of the integrated headphone jack and there's no company that sees it as a USP while people still want to use 3.5mm headphones, that the price of dongles will be next to nothing.
At the price you could just buy like 5 and permanently attach them to each pair of headphones.