RetroGaming

Why would be this be a concern?

Because companies aren't cool about stuff like this (even companies you think are cool are not always cool).

This is not direct action, but remember that this shows the thinking to avoid the wrath of a super-litigious company:

"Because the project depends on Nintendo's proprietary libraries, [Valve] have asked me to take the project down."
Speaking to PC Gamer via email, Lambert shared that he believed Valve "didn't want to be tied up in a project involving Nintendo IP."

(context note for above: Nintendo 64 version of Portal)

I wouldn't doubt the library used to make these games catching a DMCA (even if there was no legal standing for it).

I also doubt a company would even bother talking about licensing cartridges for platforms so old, though even if they did I don't think pricing would even be viable for most games/developers.

Side-note: I can also see newly-made games as an extremely clear-cut non-piracy use for emulation which sounds like something companies would foam at the mouth to prevent.