Some advantages of hiring a libjpeg developer include:
Libjpeg is a widely used library, and so hiring someone with experience developing it can give you an edge over other companies who don't have that experience on staff.
Libjpeg is open source, so you would be able to get started with development without having to pay for a license.
The libjpeg developers are very active and responsive, so you would be able to get help and support from them if needed.