Joseph that’s not all true.
Many girls decide to live in Israel and commit to the lifestyle here and move into apartments here after seminary and find a job and/or do online college. I know many like that.
I know a few others that are in programs, or sleep out with an old lady to get some extra pocket money.
At some point people feel they need to move on. I have a neighbor a few buildings over who is 26. She just feels she is big enough to have an apartment. If she lives at home she ends up getting treated like a child and helping out a lot more than she really should.
Other girls come from homes that aren’t ideal and move out early on because of that. Others (Israeli’s) can find a job, college, or a school in another city and move out for that living with cousins, grandparents, or renting an apartment with friends….
There are many reasons why a yiddishe girl would move out before marriage.