I don't intend on turning this into some sort of fight but to me your comment has big

"I don't see the problem why can't other people just have enough money"

vibes (Also I checked and an adapter costs me 12$ on Amazon). I don't think you intended it this way, so I'll shut up now.

As to my actual answer:

• Leaving it on headphones is not an option to me (I explained it above)
• Buying one for every jacket might work, but what do I do in summer?
• Please correct me on this but afaik it's not standardized
  • USB output is usually digital, while headphone obviously require an analog signal. I assume the vendors just use certain pins in the USB jack for transmitting the analog signal while keeping the rest grounded.
  • I know for certain that Samsung adapters don't work on OnePlus phones for example.

I could go on, but there's honestly no point. We're different people with different uses for our phones/headphones. I won't buy a phone without a headphone jack as long as I still have wired headphones.