How does one purchase crypto with fiat?

It's simple. Just find somebody on LocalBitcoins, find a dark alley, put on your N95 mask, and bring $5,000 in cash with you to said alley. Hopefully they'll neither rob, nor rape, nor murder you, and won't follow you home to determine where you live.

But if they do, you can rest assured that's simply KYC.

It's the on-ramp the fat cats don't want you to know.

Take 10% of that 5k, get a gun, and hire a friend to handle the transaction while you're on security.

The benefit of being your own bank is you are also your own police force and your own insurance company.

They accept a tradeoff between convenience vs security, simplicity vs complexity.