It is not about the difficulty, it's the potential consequences.
People also take care of their house keys and their wallets, but If I lose the keys to my house, it isn't automatically taken over by squatters and if I lose my ID card I can issue a new one quickly.
What happens if you lose the cryptographic key to your nostr account? Who do you call for help?
What happens when the key is lost, and the consequences like "lose all your money" or "lose your account access" are non-starters, as someone who owns a hardware key for my email account
Multi-sig wallets are even more complicated and not for normies
what happens if you lose your password? You click a link to reset it, and it gets sent to your email. What happens if you lose access to your email password?