Funny you are saying this because you are already using third party devices like your computer and smartphone that all have closed source hardware components (some even software).
So trusting computer that has much bigger attack vectors than open source hardware wallet.... that doesn't make any sense to me and to real security experts like Andreas Antonopoulos and Jameson Lopp.
I am not saying what anyone should use for holding Bitcoin, and I am certainly not supporting ledger and other closed source devices, but computers are NOT safer than hardware wallets.