Now my question is, do you think losing all of one’s coins simply because they didn’t have access to their wallet or key is already enough disadvantage for bitcoin against the local banks ?
It is not, absolutely not, I don't know a thing about the monetary policy of the country you from, but over here, people still lose the money they entrusted the banks, other trusted financial institutions to hold for them, and after back and forth dragging, going to court if the amount involved is huge, the person still end up not getting his lost money back, some do get it back if they are lucky by the court standing up for them, but for those who can not afford or know the process involved in court dealings, they end up losing their money with no means of questioning the bank.
My mother inlaw saved a good amount of money in one of our local banks here, for good five years, she never checked, after five years, she decided to go and withdraw the money since she needed it to sort out urgent matters, behold, when she went to the bank, she was told that her account was empty, she was surprised and asked them how did over $300 worth in our local currency she kept in her account disappear, this happened in 2020 and till today, this bank can not explain to my mother inlaw how her money disappeared from her account, and neither has they refunded her..
Unfortunately for her and fortunate for the bank, she's is not entirely educated, and because of this, she doesn't know how to use the law enforcement to threaten the bank to refund her her money.
So, coming back to bitcoin, the possibility of one losing access to his or her wallet through misplacement of the private key or seed phrase is not entirely a disadvantage, for people can lose their money even in traditional banking institutions.
A disadvantage is something that there is no solution to, here in bitcoin, there is a solution to prevent such from happening, and that is, to learn how to keep your wallet information safe and secure, and where you alone can easily access it, if one adhere to this, he or she may never get experience what it feels like to lose bitcoin out of misplaced private keys or seed phrase.