Though i dont know much about Bitcoin Improvement Proposal (BIP), but i think one of the reasons this was implemented is to increase the users experience with a better service.
BIPs are documents created to introduce new features to bitcoin, just like the last ones which are for schnorr signature and taproot together (BIP 340, 341 and 342). You can check the BIPs on GitHub individually.
You can find the lists on GitHub:
https://github.com/bitcoin/bipsHow can i implement a "hardened derivative" to my wallet address as a control measure in other to maximize safety of my coins?.
You can check what I have posted about it recently:
Re: bip 39 mnemonic pass phraseThe apostrophe (') means hardened, to know more about it, you can read this:
Hardened and non-hardened derivationAddresses are not hardened for public keys to be able to generate the corresponding addresses just like in case of watch-only wallet.