Answer:
Before a large corporation makes any investment decision, they carry out a cost benefit analysis. In other words, before the banks install clear acrylic partitions, they will decide if the cost of installing those partitions offset the costs of the robberies. The problem with this reasoning is that all banks have insurance against robberies, so if they are robbed the insurance company pays them. So installing the partitions do not represent a lot of benefits for the bank, but they are expensive and represent a large investment. The only way that banks install them is that insurance companies force them to do so.
