It's human nature to like what we can see and feel. Cash money may be more attractive to some people than the more common plastic or electronic forms of money used in society nowadays. However, the temptation to save your hard-earned cash in a piggy bank can end up leaving you short changed if you're not careful.
Make money with an interest-accruing account. By keeping your cash in a piggy bank, you will not be making any interest. Even if the interest rate in a bank account is very low, you are still making money by keeping your money there as opposed to leaving it in a non-interest-accruing container.
Protect your money by keeping it somewhere it can't be lost, destroyed or stolen. A piggy bank is not very secure and could easily be broken or carried away.
Avoid the urge to spend by storing your money somewhere out of reach. Piggy banks are terribly convenient for grabbing a little money here and there, but this will leave you broke.