it's Tether not Ether.. they are different.

Ok about your question.. Ripple and Tether don't have the basic properties of cryptocurrency.

They are not open source, they are centralized.. We the public cant do any mining.. Creation of new coins are monopolized by some specified people/company

Bitcoin mining is done by the public who uses their hardware and burns electricity.. but when it comes to creating new Ripple or Tether.. the people behind the coins just do it without much efforts..

Ripple or Tether are more similar to central banks and very less like Bitcoin, Ethereum, Steem etc.