how many people then immediately jump to say that they’ll wait for season 2 (or 5, because god forbid it gets cancelled) before they watch?

I never do that, and anyone who does is really overthinking how the TV box works. You just watch the shit if you think it’s interesting and you feel like it. There’s no “investment” there to worry about. If the show gets cancelled, then that sucks, but it was just a TV show. There are many others to move on to for your time wastage.