I agree with you because you are never able to know what they actually do with your money you can not ask them what they are doing with it because you trust them that your money is safe with them and in the mean time they use it for there own.
Saving and depositing money in banks are not the only option that you can choose in banks because they have a lot of options for your money and if you will choose the most suited option for you then you will not have any worries for your money. If you will deposit it then they will use it for investment that will give them more profit so you better choose other options so you will know where your money is going and get more benefits.