this also should be related to how many BTC are lost when the user forgets the password to their digital wallet(s), or they lose their physical wallet(s). Or when an owner forgot he owns BTC. (there are many states that have dormant bank accounts looking or owners), or how many 0.000001 BTC are out there forgotten by the users? Are there other scenarios that I am missing?

In the case of STEEM if you lose your password you are out of luck right? What percentage of a cyrptocurrency is lost forever?

Are there safeguards to prevent these scenarios?