Coinbase served as a more-reputable entry point due to being certified by the SEC and similar agencies since they actually set up in the US.

Personally, I got crypto back then by renting nodes on cloud services and CPU mining. The alternatives generally involved either ACH/wires, meeting someone locally, or trusting a non-US credit card provider with your $ and payment information. At the time, I was happy to take a 5-10% haircut to skip most of the risk.