Fraternities and sororities can be big in an absolute sense at big schools like most of those in those athletic conferences. However, even though they are big in an absolute sense, they may only make up a small percentage of the students at some of these campuses, so there is plenty of social life outside of them – i.e. a student who may choose to join or not join, and, either way, will not be excluded from campus social life.
This can be different from a small school like Washington and Lee, where 80%/75% of women/men join sororities/fraternities, so the social life is likely centered around sororities and fraternities, with less for those who choose not to join. Since the OP’s account name includes “ivy”, perhaps s/he may be more interested in knowing the fraternity and sorority scene at the various schools in that athletic conference; of those schools, Dartmouth is reputed to have the most fraternity and sorority dominant social scene, with about two thirds of eligible undergraduates joining (eligible = non-frosh).
Fraternities are associated with greater rates of high risk drinking.
Another consideration is that, at some campuses, the fraternities and (especially) sororities tend to be highly racially segregated. Chapter photo albums tend to reveal whether this is the case.