Even acting in good faith, you might be a counterfeiter
It is not easy to be the first one on a market, and even less to be the first one to file a patent in order to protect your invention. Also, you are not guaranteed that a competitor has not, before you, already filed a patent application on an invention similar to yours.
You are not necessarily informed of this despite your market study. Indeed, patents are not published on databases until 18 months after they have been filed and a patent is not necessarily advertised by the inventor, nor exploited.
This is the reason why, without a FTO study, it is possible that you are an infringer, and condemned as such by a court, even if you are in good faith. As the saying goes: “No one is supposed to ignore the law”!