Lots of good reasons. In hardware your costs go down and quality control goes up if you can re-use parts. It's better to have one circuit board for everything,

Lots of good reasons. In hardware your costs go down and quality control goes up if you can re-use parts. It's better to have one circuit board for everything, and enable or disable features as needed. Sometimes this means an end customer can enable hidden features, but sometimes they are left disabled for good reason (for example, too much heat for a particular mechanical design)