Some nodes require a perception amount to get a bonus for the gathering attempts (higher level nodes = higher perception requirement for something like +10% gathering sometimes). Sure, everyone likes getting lots of HQ hits, but the trade off of better HQ rates is that the market gets flooded with HQ only mats and HQ crafted items, as they become too easy to obtain. NQ items and mats get pushed off the list and/or become completely unsellable except to NPCs. A cap is better in the grand scheme.