Having a mirror is cool when you don't have a radar 😎
Checking all alpha chats can be very time consuming, and you're never really sure if the alpha call is getting enough following from their holders.
Tracking trading from Bluechip holders will always give the right signals, and can be either used to follow the trend or to confirm an alpha call if you're using Mirror or other alpha source.
Current BlueChip setup is just 6 of the most trendy/valuable NFT collections of the moment. This setup can (and should) evolve with time, and will let the community decide which collections are considered BlueChips, and therefore, are tracked.
A collection doesn't necesary need to be linked to a real collection, and could be a mix of different Artblocks Curated collections, or a group of crypto influencers if that's what the community wants.