Banks are highly regulated, while it is the Wild West when it comes to the above companies accepting crypto deposits. In the US, bank deposits are also insured against loss due to the bank being unable to pay their deposit holders up to certain amounts, and this is not true for the above companies.
Do you think a bank might have enough to refund all the customers if something bad happens? Nah, the "insured funds" is what I call a marketing trick to make people believe they're safe while in fact, they're not totally.
Also, I don't know how it works in the U.S. in such a case but if it's like in my country, the funds are insured by the government not the bank.
So imagine a bank going bankrupt, it's the government that will inject some money to make this insurance works. And from where will this money come? Taxes or borrowed money from banks.
In the US, banks are insured by the FDIC. The FDIC is funded by the various member banks via insurance premiums paid based on the amount of insured deposits. Although the number of failing banks has been low recently, due to the good economy, banks do fail every year, and those banks' depositholders have been made hold up to FDIC insurance limits. It is not a marketing gimic.
The problem with all of these services is that you are giving up control of your private keys, so you are trusting the service not to run away with your coin, or let a hacker run away with your coin. If you are receiving interest for your deposit, the service is also obviously lending out your coin to other customers, which means you are also risking that borrowers will not repay the service in large enough quantities that the service cannot repay you.
Then don't put a lot of your coins in any of them, the risk of the amount lost is mitigated but the benefit is also lowered but in the end, the profits will speak for itself. I don't think that this websites will be vulnerable as back in the Mt. Gox days, security has been a thing and I think that this websites are definitely secure.
In the days of Mt Gox, most people creating bitcoin-related services were fairly inexperienced programmers. It was fairly common for websites to get hacked because of the lack of experience, and because programmers were making websites that would likely not get hacked if not for their relation to bitcoin.
Today, bitcoin-related services are much better built, including their security, but nothing is infallible. Today, bitcoin-related websites still experience hacks. Generally speaking, the losses in relation to total customer deposits are lower, but there is still the risk of customers loosing all their deposited money.
