With direct deposits and auto payments that are available now, you may not be checking your accounts like you used to. It is important to either check your bank statements monthly or check it more often if you have online access to your bank accounts.
This morning I happended to check my bank account, after making a deposit of my paycheck yesterday. I was surprised to see it had not been posted yet. I called the bank to check the balance to make sure it was right. The deposit had not been recorded yet.
After some research they did find the deposit and it had not been posted. It is also important to check your accounts to make sure debits are not taken from your account also by mistake.
Several years ago, there was a quite large deposit made to my savings account. It turned out that it was supposed to be added to someone else's account.
If a deposit it not posted to your account, you may be writing checks or making other purchases that will casuse your account to be overdrawn. If it is the bank's fault, they may refund overdraft fees but it would still be a hassle.
Even if you have bills paid automatically, it is also important to take a look at your monthy statement to make sure you are not being billed for items you no longer need or use. There may be membership fees on your credit card that you know longer use but are still paying for.