How about, for example, the daily limit? If a thief steal me my credit card, even under threat I reveal him the code, he would be able to get a little piece of the cake, and I will be able to protect the rest easily... Hw wallet could implement this feature looking at block number, but it is not that easy, and yet no one offer it.
This is only an example of many other mechanism
to put what Franky said in a different way, with a bank you can have one or two account and put your money all there. you can't have 10 of them for example. but with bitcoin you can have thousands of wallets and addresses and use each for a different purpose!!! of course in reality you use one for cold storage, one for hot wallet and they are separate. the cold is a paper and hot can be your cell phone. the cold contains $10 million but your cell phone has $500 in it.
also as for your example, you will also encounter that limit. meaning you yourself aren't going to be able to cash out more if you needed it. so it is not always all good.
So using bitcoin or crypto currency via more than one wallets can be very safe.