It's a quite fun mode and it only coming once a year really has made Bungie's time spent on it a waste IMO. SRL, at the moment, is the sole reason that I'm logging in to Destiny. And as soon as sparrow racing leaves, I'll likely not be picking up the game again until the next content drop.
Now I know that SRL is staying in private matches, but that's not good enough. There's no way I'm going to be able to field 6 friends to play SRL, as almost all of my friends have quit Destiny completely.
Additionally, I despise using LFG sites because of the amount of toxic people there. Plus, getting 6 people together on LFG who all have good mics, connections, and personalities is damn near impossible.
So I ask you Bungie, why not keep Sparrow Racing? It's not going to hurt anyone or anything if it stays, it's just one more thing to do in the game.