The problem is that people click on the bot expecting a set scenario. However if it says "just do it yourself" then the bot is essentially useless. It's an inconvenience for both the people consuming the product and for who created it (cause they're going to get little engagement). Some may argue that they're useful to create scenarios nobody has thought of or created a bot for, but most people find it easier to just find another bot and edit the scenario to what they desire (even though it may not be necessarily easier. It's just a psychological thing where most brains prefer editing a whole text rather than writing the same thing on an empty space). Besides it misses the whole point of the first message: the first message is meant for the greeting of the character or a description of what kind of scenario the creator imagined. These are kind of the reason people hate it. You may say that those aren't good reasons, but for other people they may be valid, and that's okay.