Most of us have been raised with some variation of "Never a borrower nor a lender be". But none of us has been told that Plotinus (Shakeseare's Hamlet) was a bit of an old fuddy duddy.
It would be wonderful if we could always pay cash for everything. That would suggest that we were always able to live within our means and that we could always access more cash whenever we needed or wanted something that exceeded our regular income. Unless we have a trust fund or a large supply of "matress money", this will never be the case.
Borrowing is necessary 99.99% of the time when it comes to housing. For a lender to feel comfortable with you as a borrower, he needs to know how you handle the repayment of your debts. Having made regular payments on a few credit cards for at least a year suggests that you are a good risk. That is crucial if you never owned a home before.