We add it when the community might not have heard of the startup or known they did YC. Airbnb, Dropbox, Stripe, Reddit, Docker, Twitch, Zenefits, Instacart etc. don't need it (and indeed, consistently don't get it).

To be fair, I've been following YC for 12 years and I didn't recall that Instacart was a YC company until I saw the parent's comment.

There are just too many to keep track of, even for the big guys.

That said, I don't know that who they raised money from is particularly relevant to the story.

+1