Do you think constant Firmware upgrades on hardware wallets are their weakness? I have gone through some firmware upgrades for some hardware wallets (Ledger) and I have to say for someone with good technical knowledge, it was not a good experience.
Yes I think it's a big weakness, especially if hardware wallet firmware is closed source like in case with ledger devices.
In this case you would need to fully trust developers to be honest, and won't make any mistakes that could allow hackers to steal your coins.
With open source wallets you can always verify the changes, and other developers can do the same reporting some potential issues on time.
Perhaps this is a big weakness, but for the average user (most of them will be) it doesn't matter if the source code is open or closed, because he will not be able to read the code or changes to it. In the case of a closed source code, you will have to trust hardware wallet developers, and if the source code is open, then you need to trust independent developers and enthusiasts who check the code and changes. In both cases, ordinary users are forced to believe completely strangers. I think it looks like a religion. There, too, "users" can't check anything themselves and they can only "believe" in one or another confession.
Another important fact. People who buy HWs want to make a minimum of gestures: they bought a device, threw crypto into it, and use this device as needed. Will most of them follow the news and technical blogs where independent developers will post their research into the open source of HW? Even if a vulnerability is found in the code, such users will be the last to know about it after a long time, if at all they become aware of what happened. Until the balance on their device is reset. Therefore, I assume that from the position of an ordinary user, it doesn't matter to him which code is open or closed.
They are more interested in HW appearance and the impact of advertising.