"what was wrong with 'Save' and 'Save as'"
Quite a lot actually. This is a personal bête noire and is a very good example of how users like to stick with bad solutions they know rather than good solutions they are not used to. People are used to "Save As" but it is bad for so very many reasons. The problem being it combines two action that should be separate, duplication and renaming and, horror of horrors, it is often used to save versions of documents. Why is this bad?
1. Duplication where there should be one canonical version. Duplication results in multiple versions of a file often badly named. Far better to have one canonical version with versioning build in (as all Apple apps have had for some time - only many users don't think about it). "Save As" can too easily result in many versions of a file across the filing system.
2. Uncertainty as to what is contained in "orphaned" versions. When "Save As" is used, an old version is left behind. So if it is used to duplicate a file, was the previous file saved first? Very often the user doesn't remember. Is there any sensible coherent version of the file in the old version? The user may well have forgotten when it was last saved. Consequently after using "Save As" users tend to distrust the earlier versions unless they have a really highly developed habit of saving before using save as, or a disciplined sense of what the file contained when it was last saved. This undermines the value of Save As for the file duplication use case. But also results in file detritus. We've all been there. It's horrible.
3. Bad version naming. If used for versioning, doing version naming in a file name is an extremely bad way to do it; is a very 1980s solution we have the tech to move way beyond now. Version naming is more difficult to do well and more prone to error. Maybe modified dates can be used to overcome any possible user introduced inconsistencies? No relying on modified dates to determine version precedence is dangerous. If you keep to versions open and modify an earlier version, even by mistake, the modified dates are no reflect version order. My personal "favourite" bad file version practice is when you see files named things like "xxx Latest" or "xxx Updated" (though I acknowledge this isn't an argument against Save As per say, because you have to be a special kind of stupid to make this mistake).
So sorry I disagree, Save As is one of the worst user "I like it" habits in the history of personal computing. We really are far better off with dedicated and distinct duplicate and rename functions and with proper version management (which so many people ignore) built in. Alas, people like to stick with their habits. Personally a drink too much.