I think there's maybe a secondary point here around where people who regularly go to Saints games live. I'm pretty sure there would higher percentage of Saints fans living outside of Perth than there would have been ten or twenty years ago. Due to lack of opportunities in Perth, folk, including myself, have left for jobs, university etc. You only need to look at a bus with 30+ people in it leaving Edinburgh to go to Greenock last week to evidence this.
Clearly if more of the Saints support live outwith Perth then you have the knock-on effect of lower demand for spaces on buses leaving from Perth.