when was archive project introduced in project settings?
According to this link from 2017: Archived projects are only visible in the admin area (#30745) · Issues · GitLab.org / GitLab FOSS · GitLab
so in short, a long long time. Why ask? Is it really that important how long it has existed for? More important is, that the option exists 
- it is widely used on github
- in my experience i seen only two repos on gitlab
All my repos on Gitlab.com has it, so I don’t understand what your problem is? Perhaps you can explain in more detail what your problem is?
- list is empty_ Ian Walker · GitLab
- i visited above page before & after login…
Because my repos are private, and you wouldn’t have access to be able to set archive option anyway even if they were public - nor can you see archive option on public project. Only owners or possibly maintainers can see that.