> MPEG is not free. A license is required for using MPEG.
For MPEG-1 this is not true anymore. All patents have expired. It's also far less computationally expensive and easier to implement/integrate than more modern codecs. This makes MPEG-1 a "good enough" solution for (e.g.) short video clips in a game.
Disclaimer: I wrote pl_mpeg[1], so my opinion is biased.