He knows all of my passwords, I have nothing to hide.
That isn't the point.....the point is respectful boundaries and personal space/privacy
I doubt he thinks you're cheating or the like.....more like he gets a perverted thrill at the thought of watching your every move, hearing every word without you knowing.
Like the men who take nude pics/videos of their partners without their consent whilst they're asleep, there is no reason why they do it.
They do it for the kicks, the sense of power and control it gives them to be a fly on the wall, knowing every tiny thing you do, being privy to your most personal/private conversations with friends/family/gp etc.
Any info gleaned will be used to manipulate you because they're already 'one step ahead' of you and have had time to formulate their plan.
It can be used to gaslight you.
If he's cheating/planning on leaving you then this 'insider' info would be invaluable to him.
You'd never be able to trust your instincts/intuition regards him because he'd have beat you to it and learnt how to cover his tracks
He's basically violating the last bit of personal space/privacy you have - and he's point blank lying to you about it.
He doesn't value you as an individual with her own rights and freedoms cos he owns you in his warped mind.
Do you have any issues/problems in your relationship?