Great thread!
Lots of interesting pinions, which, of course, are varied as there are posters.
Such an individual decision all around, kind of like what songs we may choose to learn.
I do think, in general, that is beginners barely need more than one guitar. But it depends on what we are interested in learning. For what I want to do, I would argue I āneedā two guitars at least, a classical nylon string and a steel string acoustic. Some may want an electric of some type and an acoustic. These are different enough instruments that a beginner may still benefit from having the options as they learn. More than that (for a new player like me and many of us) is because we want to, can afford to, enjoy the gear, like playing with different toys and so on. All valid reasons to have more fun stuff. But need? What I NEED is to learn to play the dang things.
As players advance, though, the nuances they appreciate, the expression they want to achieve, they notice the playability differences, need alternative tunings, backups, the list goes on. They are artists and the varied tools they use may impact the art they produce or at least the feeling they get from producing it. Some may not use many instruments, and there art is built around that. Others have lot such a life around their instruments that they enjoy having a variety and collection of their interest.
Currently I have 5 guitars. Two classical nylons, one of which is a nice but beat up guitar I am not afraid to take places, like up to the mountain condo where is a drier than the desert. Two steel string acoustic guitars, one a short scale 12 fret finger picker and the other a longer (normal) scale 14 fret narrower my strummer. The 5th is a strat. I am not playing it really at all, but keep thinking I will. It is quite nice since I rebuilt it well, because t it isnāt worth anything to sell so I may as well keep it. I probably donāt need the longer scale acoustic, but I like it and. Enjoy playing it. If I need the money, it would be the first to go, but I donāt. It was nice to be able to have one extra to lend to a friend for a while as well.
At this time, any additional guitar would be just because I want it, so I am refraining. It is a struggle as I am also one of those who just plain old like gear.