Do you have any proof that the hardware wallet providers have access to your private key?

No I don't have. And I do not intend to spend my time becoming a top expert in finding the evidence before deciding not to use it.

Most hardware wallet uses a standard method of generating seeds. It is widely used and with the seeds, you can import it into LOTS of wallet or just simply write a script to extract it yourself.

This is where I said you argue for the sake of arguing and ended up missing some of the points. Oh well, so I guess the recovery seeds have no problem after all and rely on no 3rd party. Well, guess I am going to protect the seeds after all. But NO, I am going to protect my private keys directly instead. You are in fact avoiding the point that recovery seeds need to be properly secured as well. By avoiding that point, you are indirectly implying the recovery seeds need not be secured nor elaborate how to secure them.

Jesus, I don't even know if I should continue but oh well.

Don't continue, then.

How are they helping you to secure when you are free to review the code to find and test for bugs? If you don't like to rely on third-parties, it might be better for you to write your own OS or wallet.

Duh, why should I need to write my own OS or wallet when I already have wallet generators like Electrum to do it for me? And do I trust Electrum? I don't need to if you understand my points accurately instead of arguing like a very smart guy.

Point 2 and point 2.

Whatever your point is, does not invalidate my point that if a person can secure his seeds well, he might as well just do it directly with his private keys. And besides, do you really expect everyone to be a tech savvy that they are able to write their own OS, etc? Be reasonable. What I am offering is a way that is far less complicated that an average Internet user can use.

It's kinda hard to hack a wallet when the keys are never exposed to the outside world.

Hard to hack? My approach is not even hackable.