The purpose of taking a "secured loan" is to build credit. This might be done by someone who had a bad stain on their credit history such as a bankruptcy or foreclosure, or possibly by someone just out of school (presumably with few or no student loans),and no credit history. Not everyone needs to, or should do this, however.
The advantage for a borrower is that s/he gets to create a record of repaying a loan that will partly mitigate the bad credit history. The advantage for the bank is that it is "no risk," because the savings account is the security for the loan. That would make it willing to "lend" to a bad credit risk.