Hello Poinoichou64
We Swiss use our trains like other nations use their buses or metros in cities: go to the station, check the board for the next departure, go to the platform, hop on, find a seat, have a ride, get off, done.
A ticket with a seat assignment would kill any flexibility currently allowing you to take an earlier or later train. Again, you will see how it easily it works once you are on-site.
Here you pay for the transportation, not for the seat - as in most European countries on domestic routes. The same way it works in Germany, Austria, and many other European countries.
Those who want to make an optional seat reservation can, yet it is not included in the ticket.
See our guide about seat reservations for more clarity:
https://community.sbb.ch/blog/23887-demystifying-seat-reservations-on-swiss-trains-a-comprehensive-guide
Kind regards,
Roland