We have playtested these types of effects and they can sometimes have the effect of removing hope from your opponent. If you could see your opponent's hand, the game would be less fun to play, not more. It's ok to play a big minion and have it get to destroyed. It's less fun knowing you can't play your big minion in the first place. I think it's less frustrating when your opponent is holding minions you already know about, than when they are holding removal or AoE.

We sometimes end up in this space with cards like Thistle Tea and bounce effects on minions with Battlecry, but it's something we try not to do too much of.

Also, I want to mention how much I appreciate you phrasing this question in a way that invites conversation. There are definitely pros and cons in this discussion, but I prefer coming from a place of "let's learn more". I love working with the community to share thoughts and ideas for how to improve the game. /salute

You're right, it's subjective. One of the things that makes someone a designer is their ability to run a subprocess that keeps tabs on how and why they are feeling what they are feeling while gaming. "I am engaged right now. Why?" "I am frustrated right now. Why? And is being frustrated bad or good in this situation?"