Unfortunately it's exceedingly difficult to be both a great painter of landscapes and a great portrait artist. Or to be an exceptional travel writer and an author of thrillers. For similar reasons, developers end up specialized toward specific targets, across the dimensions of both deployable device(s) and targeted subject matter.
Sure some of this happens because we get typecast, but mostly this is due to time limitations: to excel at user interface design or a particular IT subject matter you must invest the effort to become totally immersed and familiar with it.
Yet as an artist, it also benefits a developer to expand his repertoire to adjacent presentation formats and related business fields. This is easiest to accomplish at the fuzzy borders of both. When you are designing a web page, see if you can also do a "light" or a mobile version. If you are working on CRM development see if you can stretch into analytics.
The main benefit of this -- aside from the obvious increased skill set to offer employers -- is that (like an artist) your new experiences will cross pollinate with the old, making both stronger. This is only beneficial to a certain depth however: if you attempt to be a jack of all trades you will find that you are a master of none.
