Sure, some commercial robots are just out and out scams. For instance, an unscrupulous vendor might realise that his EA would have blown up an account on a certain day, so he will hardcode any bad dates into the EA to prevent them from taking trades in the strategy tester on those dates.
Unsuspecting buyers will see an equity curve produced by the tester showing a steady rise because it won't have taken any of the fatal trades. Anybody caught by a scam like this risks not only losing the purchase price of the EA, but also the contents of their account when the EA inevitably blows it up at some stage in the future!
In my view, this is just downright deception and such products rightfully need to be exposed for what they are!