is there any real purpose to learn C?
Why not, some people learn Old Greek just for fun.
Experience is king in software development. Knowledge is invaluable, question is what kind of knowledge.
A language is just a tool. Way more important is the underlying language independent knowledge. That's what tells apart a good programmer.
If you interested, just do it. Grab a book and go twiddling a bit with C. After that I would rather recommend to dig deeper into algorithms, data structures, software architecture, patterns, etc. Always stay open minded, question what you are doing, learn how to efficienctly complete projects, choose a language when it's appropriate by objective facts, etc.
At the end of the day, whether C, C++, C#, or Java, its still the same old crap...