Having any amount of cash on you including a large amount of cash is not illegal as long as the cash you have on you was made legally.
However having a large amount of cash on you is not a good idea since you could be robbed of it or lose the cash and not be able to get it back.
If your money is in the bank you'll know where it's at and you won't have to worry about getting robbed of it.
Plus it can make the police suspicious if you're carrying a large amount of cash on your person because drug dealers carry a lot of cash and the cash could be seized until an investigation is done.
But if you're not dealing drugs then the cash should be returned to you although it'll be a hassle especially if you have the large amount of cash with you when driving around.
It's best to keep the cash in a savings account where your money can actually grow into larger amounts of cash overtime due to the interest.