The real reason they want depositors is fractional reserve banking. If you deposit $1, they can go borrow $10 from the federal reserve, loan it out, and be making interest on $10 of created, loaned money.
http://bankunderground.co.uk/2015/06/30/banks-are-not-interm...
tl;dr "banks extend credit, creating deposits in the process, and look for reserves later"
http://www.debtdeflation.com/blogs/2009/01/31/therovingcaval...
The document is about reserve requirements for deposits. Roughly speaking, if a bank takes in $100MM of deposits, it has to keep 10% of that ($10MM) in a way that's easy to access (either as cash in a vault, or as a deposit at the central bank). That way, if a depositor wants their money back, the bank will probably be able to give it to them.
If a bank has total deposits of less than $14.5MM, then the reserve ratio is 0%, instead of 3% or 10%.
1) The bank's loan assets go up by $X 2) The bank's deposits go up by $X
Deposits are part of 'net transaction accounts'[0] so the bank would now need to hold 10% of $X in additional cash (e.g. in their vault).
So, it seems like the bank can create a loan of $X with just $0.1X of cash. Hang on, though. This assumes that the borrower just keeps the money in his bank account, which is unlikely. When she withdraws the money to spend it, the bank's reserve requirements go down by $0.1X (good) but they also need to pay out $X of cash (bad). So, it really did cost them $X to make $X of loan.
Now, if they have a CDS related to this loan, then they are insulated from the risk of default. But, how is that relevant to reserve requirements?
[0] "Net transaction accounts are total transaction accounts less amounts due from other depository institutions and less cash items in the process of collection."