I think is because of Apple iMessage, since a lot of Americans gave iPhone and they use iMessage, which sends SMS when the phone on the other end is not an iPhone.

When dis medium become a paywalled site?

Do writers on it know that you can only read 3 articles before you are required to create an account and login? (like pinterest)

Use a private window to get around this. It's not a very advanced mechanic (yet).

Cookie Auto Delete solves the issue