I do so because I am an Apple user - this is being typed on a mac mini. I also own other Apple hardwares.
I also advocated for Apple hardware within my family & friends to switch from Android to Apple quite successfully (I am the IT guy in my circle). I did so because I would like to believe their commitment to privacy they have publicly stated. (Tim Cook being Gay adds to that trust because he understands that privacy is not just about hiding secrets but protecting ourselves from political persecutions by those who do not like some part of our identity - whether it be regional, gender, political, cultural, religious, sexual etc.).
It doesn't mean I trust them blindly or completely or will allow them to screw my customer rights (like right to repair, and OWN my device). Would you?