Why does witness data get a discount while UTXO data doesn't?
The answer lies in how and why SegWit resolved the quadratic hashing issue.
Andrew Poelstra discusses with nostr:npub1az9xj85cmxv8e9j9y80lvqp97crsqdu2fpu3srwthd99qfu9qsgstam8y8 the reason for the witness discount in BR029.