Is Instagram geared towards rich people?

I was on Instagram yesterday when it suddenly logged me off and demanded to "add phone number to get back into Instagram." And underneath it said, "We will send a confirmation code via SMS to your phone." I don't have a mobile phone. Whenever I go to Instagram login page it gives me that message. It doesn't give me any other options. If I log off and then click on "forgot my password" and request a login link to be sent to my e-mail, it says "no users found" or "feedback required" or transfers me to the above-mentioned interface. I tried logging in from my old computer (and another browser), with the same results.

Is Instagram meant to be an elitist social network geared towards rich people who can afford to buy an iPhone and pay for it every month?