Most leisure passengers these days make purchases based on price, and Southwest isn't necessarily the cheapest any more. Personally when I fly to Seattle to visit relatives, I prefer Southwest because they have two included bags and we're not necessarily going crazy over being together with the open seating policy. They also have more flights out of Oakland which is more convenient for me and where there's less issues with weather delays than SFO. However, I'm consistently getting cheaper prices from Delta out of SFO on one of their regional partners like Skywest.
Amtrak used to be an alternative that many people chose because of the flexibility. They had a policy where a no-show could get a refund minus a 10% service fee, or full credit for another ticket. Then they switched to where it had to be cancelled before boarding. It got really tricky because it's not typically like an airline gate where everyone must go through a single line. Sometimes people end up boarding and a conductor doesn't reach them and after a while they're counted as no-shows, where the remainder of their trip on the same reservation is cancelled. But even then it was generally really flexible where someone could cancel at any time up to the arrival. They've got new management now. The current leader was CEO of Delta Airlines and has gutted everything that really differentiated Amtrak from airline travel.
