I love Silvercar but I don't think it's the best value for rentals that involve less than ~3 hours or driving per day. But to each their own, of course.
The main purpose we rented this time was to be able to go to the Coldplay concert down in Santa Clara without having to pay the outrageous surge rates on Uber/Lyft to get back to the city afterwards. I am a fan of their app, and really enjoy their "no BS" approach to things.
We didn't honestly need an A4 for that purpose, and going with Avis would have been a better option since we have Avis Preferred. Far cheaper and minimal BS with their select-and-go service. I'll likely still use Silvercar for longer trips though.
Just my opinion but I don't think that "needing" an A4 is a critical component of their business model.