Why aren’t banks typically opened or operated inside shopping malls?

There are many reasons behind this, having recently consulted on a project that was very similar the rationale was as follows (your mileage may vary)

1. ATMs do the job very nicely
2. Deposits from Shop Owners, etc. is already taken care of by Cash Management of various banks. The cash management is already insured and offers local pickup, so convenience and security is already there.
3. Majority of the crowd profiled were those who would need to withdraw cash, versus a deposit. The ratios are typically like for every 600 people withdrawing money, 1 would like to deposit money.
4. Space considerations (vault, etc.), leasing space is too expensive to run a bank branch in a mall, where the ROI just doesn't make financial sense.
5. Smaller, booth like presence would suffice
6. Malls represent a great avenue for advertising, but not for account opening. Only 2% of the people profiled and queried would actually be interested in "stepping" in your bank, less than 20% of those that enter your bank would be looking for an account opening requirement.
7. Most spaces available for banks in the mall, would not have any outside approach, the only way to access the bank would be to park and walk inside to the mall.
8. Most businesses already have an established banking presence, so trying to convert businesses to bank with your branch offers little incentive (See # 2)
9. Nearby businesses around the mall, found that venturing inside to a mall for banking, was not something they favored (this was a surprising point for us).