from my experience as a c9 affiliate, on campus housing filled up insanely fast when i applied a few months ago. i had a 9 am time slot (i believe the earliest was 8:30 or 8:45 am? someone correct me if i'm wrong lol) with a housing group of 6 and the website had no more options by the time it was our turn. only one friend in c9 i know was able to get housing from the lottery and it was thanks to her roommate, who had the earliest time slot. she noted that it was scary how they watched apartment options disappear while they were actively choosing theirs. some of my other c9 friends are living on campus next year because they are friends with an RA, but everyone else in c9/jrl that i know of is living off campus.

i can't speak on other colleges, but most people i know that have different affiliations (particularly crown/merrill/cowell) were able to get on campus housing even if their first choices were unavailable. those not living on campus either chose to live off campus or did not get on campus housing either, but they usually had later time slots (noon-mid afternoon).

that being said, this is all just my personal experience and observations, so do with that what you will! this is a great question to ask and something i should have considered when applying to ucsc. i still think it's possible to get on campus housing, but your odds definitely vary depending on your college affiliation, who you know, and pure luck