PKY
What’s the hassle of buying a ticket at a vending machine or in the SBB Mobile app, compared to the lack of paperwork at airport immigration/customs when arriving in Switzerland in comparison to other countries such as US, Singapore or even - heaven forbid - Australia?
Anyway, within local fare networks covering shorter distances in Switzertland, you get a zone-based ticket, as opposed to the Zurich-Luzern point-to-point ticket (longer distance / different fare networks) which is valid the entire day.
Single journey zone tickets in the ZVV network (around Zurich) are valid between 1-2h depending on the number of zones/covered distance, while return journey tickets are valid 24h.
Therefore, if you don’t mind the double price, simply buy a return journey ticket instead of a single journey one..