They don't work the same way they used to though. Since old school PSTN hardware is being replaced with VoIP, there is a hacky protocol called T.38 which does just enough to convince each side that it's talking to a real fax, and decodes and forwards the data over IP.
Circuit switched class five offices are still very plentiful though, and DS3-based transit networks are still nationwide. So if you want it, you can absolutely still experience phone networks without voip.
I doubt that very much. Pretty much no telco has used circuit switching in decades. Everyone moved to packet switched network a long long time ago. Even if you have a Real Landline, it's just plugged into a VoIP box at your nearest telco branch.