Only in small companies do everyone need to know everything, and again, only if that company even does everything.
You only need a transactional database for transactional system. Sure, your shopping cart needs ACID transactions. Bit if your website is letting people upload LolCats all day? Not so much. NoSQL in 2014 is the general case, not the specific one.
And lol. The vast majority of developers at Google don't do SQL, most don't know SQL (its not taught in big name schools in any mandatory class and they don't use it most of the time, why would they?), and its usually not part of the interview.
I work for a multi billion dollar e-commerce site. I've been a DBA, I worked on transactional portion of websites for a decade, but for my current role, I never have to touch the database. There's 40 million lines of code on top of anything data access related...hundreds of people are working on that part, and only a handful are working on the section that actually touch the various databases (we have probably 50, totally a few petabytes of data...and its only a few teams that ever have to deal with them. I'm not one of them).
Any meaningfully large project will require specialization, and the database is just a tiny portion of it. And that's if there's even a database.