It's also important to note that more and more community colleges are offering four-year degrees that can be completed entirely on that campus.
This article from last April says that 26 states have authorized their community colleges to offer four-year degrees, and that 27 of Florida's 28 two-year institutions now offer four-year bachelor's degrees. There is a growing segment of the college-going population that stays at a community college for their entire higher education experience, and that segment is not being served at all by the Panhellenic experience. There are even some schools, like
Richard Bland College, that are two-year institutions that offer the full residential college experience and have guaranteed transfer pathways to four-year colleges. I do think transfer affiliation issues would have to be worked out first before a sorority starts plunking down chapters at every associates' degree-offering college in a state, but that's up to each individual sorority to decide what works best for their member experience.
Re: Titchou's excellent point about where expansion has been happening in the past 15-20 years, there are only so many established prestigious universities with fraternity and sorority life, and only so many that are hospitable to new chapters for a litany of reasons, and only so many that a given sorority has the local resources to coalesce around a new chapter. If ADPi had to choose between starting a new chapter at University of Alaska-Anchorage or Palm Beach State College, I know which one would be easier. Additionally, chapters at state and community colleges wouldn't need housing so they'd be much cheaper to start than a chapter at Big State U that needs a McMansion to be successful.