Also like you ask there's no harm if public key in known. So why to hide it? I know this BUT it wouldn't hurt to conceal it for privacy reasons does it?
We don't hide it. It's simply that you can lock coins behind some script types without revealing it, but it is revealed after you unlock those script type. Concealing it brings no additional privacy since the only thing an attacker with your public key can work out is your address, which is public knowledge already.
See if the bitcoin devs didn't care about it they wouldn't introduce Taproot which essentially enables multi-sig wallet to conceal their pub keys and aggregate them into 1 key and no one can find out the real pub keys which is great IMO and helps in privacy.
The privacy gain here comes from not being able to tell if the address is multi-sig or single-sig, not from obfuscating the individual public keys. And indeed, taproot addresses are simply an encoding of the (tweaked) public key, so any time you use taproot your public key is exposed.