[256DEV]

So I actually do have a version of my API that doesn't require any sign up at all for the users that prefer this!

You can see it here: https://www.exchangerate-api.com/docs/free

That said, as much as some users want an open endpoint with zero authentication there are many others who want an actual account, commercial support, high availability, more features etc. These users are also the ones that pay for development, infrastructure etc. so my service has to be 95% built around the flow that includes signup.

[StavrosK]

Yes but you can let users sign up with their API token at any later time.