The TIOBE Index represents the world of computing at large, including embedded development, industrial, financial, automotive, medical, hardware, etc. This is why C and Java are at the top of the TIOBE index and I'll argue will be there for the next 40 years, and doesn't mean that any language which is not C or Java are unpopular or niche. Ours might be a small percentage of total computing, but would you argue that web technologies/the Internet as a whole is a niche?
There is a reason the embedded world still uses C, and there is a reason the web world doesn't. Using the TIOBE index as popularity contest is misguided.