Storing your wealth in the safest available way is certainly not irresponsible. I think it would be the opposite.
Giving your wealth to a stranger, with a history full of strangers going bankrupt and getting hacked, is certainly not the safest.
Meanwhile, storing your own physical keys involves risks, and people lose their Bitcoin this way all of the time.
Because they do it the wrong way. They are reckless and store them on Internet connected devices, with closed-source operating system, potentially affected with malware, and do not even verify the binaries. People who secure their wallet, the right way, and have lost them due to $5 wrench attacks are outnumbered by the number of victims who lost all their savings on Mt. Gox, FTX, BlockFi, Kucoin, Bitfinex and an endless list of others.
You're mistaken in the sense that you think a third party safeguards your wealth with legislation, as with houses or bank accounts, but this is different. It's easier to steal, and there is no insurance.