If need to use an API, needs to do: user creation, top-up some money, create a token, store the token somewhere, pass it to the agent... and later renew the token...
With a blockchain, no need for all of that. And you can only pay for few cents, no need to top-up a full 5$ min for each services. If you have dozens of services that you need to reach, the benefits start to be interesting.
That all happens in Lightning Network too, it's just called different things. You need to create a channel (create an account, create a token) locking up a certain amount of money (topping it up), and obviously you need to store the credentials for the channel (store the token), and renew it (renew the token) or close it (refund unused credits) every week - that means opening the app at least once a week or you lose your money - otherwise your partner gets all the locked-up money.
This is why lightning hasn't and won't catch on. It's very interesting technically but terrible UX. Not to mention problems with scaling those channels and finding valid routes.
USDC is much simpler.
Well, your crypto wallet is also tho materialising from thin air out of nothing... You need to set up things top up wallet, take care of keys etc...