Money seems as good reason as any to me!

If somebody develops CAN or TCP/IP or whatever, they put a lot of their time and energies and development into it - and you then expect them to publish the code for everone to use for free? So that for no effort on your part you can then build something and go into competion with the person that did all the work. Most people that have put in the time and done the development have done so because they have mortgages to pay and families to feed...