Right, it's meant to be driven. Plenty of people in Canada, Norway/Sweden/Finland etc have them and drive them on roads where salt, sand and small rocks are used. Is it a harsh environment? Yes, absolutely. Is the Tesla different than other cars? For the most part no. There have been cases of lower body paint damage on roads around here in the first years. People started installing ppfs, and Tesla delivered mud guards. There have been such cases on other car makes too as far as I know.
Around here many people do a full ppf and they rustproof (oil) the car. I went for half ppf and good mudflaps. None of that is essential. With anything else, the level of care you apply to something will influence it's state in a few years.