I do not get why some HWW manufacturers recommend entering a passphrase on *every boot*, compared to storing it on the HWW itself.

The entire point of a HWW is to securely store your keys, and the PIN is a much stronger mechanism than passphrase. (because of the limited tries)

So you could store the passphrase on the HWW without losing security, and keep it separate *for the paper backup*.

But some dumb vendors say for "additional security" enter your passphrase every time. Which is basically "we do not trust our PIN mechanism to be secure enough."

Such an implementation also increases the risk your passphrase gets stolen, as you use it much more frequently, and so will most likely store it in a more convenient but less secure location.