I understand your frustration, but we do not yet have a universal platform to facilitate OTP. There is also hesitation about using SMS for OTP as it is trivial to take over a persons phone number. Not everyone has a smart phone, myself included. I believe the issue is a bit more complex than passwords vs. OTP.

Also there is the issue of not all services not supporting OTP, SAML, OAuth, etc. Things are slowly evolving in that direction, but there will be services that require passwords for a very long time. There are still services that do not even support encryption.

All of that said, you could certainly provide an incentive to your user base to use MFA/OTP. Blizzard did this by giving players more inventory space if they enabled SMS and hardware tokens on their account. That won't convert everyone and they still have to support password algorithms.