if every airline only promoted on seniority / date of joining then, should you be unemployed you will have to start again as a junior F/O at a new company.
As a profession do we think it fair that someone with 20+ years in command possibly a TRI/TRE etc etc has to start again at the bottom of the pile.
Didn't you answer your own question?
It is a big bad capitalist world out there NSF & co. thats life, stuff happens, no such thing as a free lunch, you cannot beat the market etc etc!!