There's another angle - vendors also make money from support contracts, and fear that if they gave you the ability to get support from anyone (even yourself!) t

There's another angle - vendors also make money from support contracts, and fear that if they gave you the ability to get support from anyone (even yourself!) they'd lose that revenue stream. For more consumer-oriented products, manufacturers don't want to deal with supporting products that have been modified... (well, they don't want to support them unmodified either, often as not).