What are the advantages of a hardware wallet vs an airgapped mobile phone or computer? It is the memory quality so much different from a good RAID? How are people with multiples of coins and over 100k storing their keys?
Hardware wallets have Hardware Security Modules which are specially designed hardware for storing and securing cryptographic keys. In general, HSMs are better than generic laptops or phones as HSMs are often validated for HSM standards like FIPS 140-2. These standards require that the HSM meet certain specifications for security, tamper resistance, etc. The use of HSMs means that the private keys can basically never leave the device.
Hardware wallets are also much easier to use than an air gapped machine and less prone to human error (e.g. accidentally allowing the air gapped machine to go online).