Is Defrag still necessary?

Our policy is to run Defrag on the database about every quarter. This is running 12.0.1.2

I'm a developer not a DBA, but I don't remember any of my previous employers ever defragmenting the database, let alone every quarter. 

We're not even that high of a volume database, compared to many other places I've worked. 

Now, it's possible that defrag was done without my knowledge before, but is this common?

I do remember the DBA thinking about table extents and such before..

The outsource company who helps maintain our system said that this is necessary for performance.