Obviously, most skiers do not read epicski threads and if instructors here see 50% of their students (or clients) tip then there is a huge education piece that needs to be addressed. I think the PSIA should do something to either get a better wage or salary system in place for its members or at least put some type of public awareness campaign to highlight the situation for clueless resort patrons.
My biggest issue is that high level professional instructors should not be compared to waiters or waitresses in a resteraunt. That's a very different industry with a pay model set up for servers to rely on tips for the majority of their pay, and it's common knowledge for the general public to know that tipping servers is expected. Maybe a better comparison would be a highly experienced concierge in a 5 star hotel, or a tour guide, or a tour helicopter pilot, something that isn't run of the mill which requires an investment in time and resources to achieve a higher level of competence or certification.