First off there are plenty of people in all different jobs that want to take the easy way out and will do this by just copying what somebody else has done. Companies like Bosch for example produce a lot of the electronics/electrics for the OEM, they normally do this by designing, producing, testing etc to the manufacturers standards. I know for a fact that bosch had to produce a window switch for a particular model car, but according the the car manufacturer it had to last a minimum of 1 million useages, Bosch had to spend a large sum of money just to build a machine to test just this 1 switch. This cost has to be factored into the final product costing. Along will come some aftermarket company and just buy 1 switch and then copy it for a far less cost and normally with cheaper parts, they saved money by not having to design it or test it, they just make them in bulk and sell it cheaper than the original part. A tuner may spend a day tuning a car, but may have spent countless hours over years and a lot of money, developing their knowledge to what needs to be done and how to get it done. The last thing they need is someone to buy 1 of their tunes and set up shop as a competitor and use this tune in all cars selling it as a complete custom tune and at a far less cost. It would even be worse if the tuner supplied a good tune and the owner had access to adjust the tune, went out and changed it and did engine damage and not admit to the changes, reputations can make or break a business. Most tuners have put a lot of effort into what they do, (some don't) they may have something different to the next person and believe that is worth something to them, intelectual property I think they call it. Sorry if I went off topic, but there can be lots of reasons and everyone may have a different one.