No down payment?  This is a key reason.  Data from the Federal Reserve’s Survey of Consumer Finances show that the typical renter has only $3,000 in financial assets (cash, CDs, bank accounts, bonds, 401k or IRA).
"Adults who rent their homes are mostly renting as a result of their circumstances rather than as a matter of choice. And many see their financial situation, such as existing debts or their inability to afford a down payment, as a barrier to owning a home.  About two-thirds of renters (65%) say they are currently renting more as a result of circumstances, such as not being able to afford to own a home right now, while 32% say renting is a matter of choice – they could buy a home, but they choose to rent instead."