I suspect it's a combination of support, documentation, and trade secrets. I've worked with numerous vendors over the last decade and the support strategies var

I suspect it's a combination of support, documentation, and trade secrets. I've worked with numerous vendors over the last decade and the support strategies vary dramatically. Some vendors put up very nice datasheets, manuals, source code, etc, while some give you almost nothing at all, and instead ship an engineer with the product to help you design it in. The rationale is that these chips are very complicated, applications vary dramatically, and it's sometimes better to increase the quantity of manpower (in engineer form) for your favorite 5 customers (that make up most of your market anyway) rather than to increase the quantity of documentation so that you can also sell to Joe & Jane Hobbyist.