a lot of people dropped their sororities?

I haven't heard this, but there are always girls who drop when they get to doing their first formal recruitment. A lot of the time, recruitment can bring out the worst in older members because they're so concerned about getting a good pc. Other girls drop because they realize their values don't line up with how superficial chapters internally are about accepting girls. Some are uncomfortable with the formal process & all the things that are said about PNMs. Some just a coincidence or didn't like their first year or semester in the chapter.

Sometimes it's for financial reasons. Like you can get fined if you do not go to certain mandatory events which are expensive. Also, some people just do not see themselves in the sorority anymore. But once you get initiated, you can never join another sorority so everyone needs to choose wisely to avoid this.