Shouldn't might be harsh, maybe isn’t economically feasible is better. An Engineer’s time is valuable. Far to valuable to be spent on a problem solving excursion for a low probability prospect. Instead they should be Business solving. What is business solving you ask?
Business solving is monetizing your problem solving skills. In some circles it is call consulting. If you find yourself giving away your time and ideas and you are not charging for either, stop. You should be able to tell someone how you can help them fix their issue without giving it all away.
Give your engineers big juicy problems they can solve, but after the check has cleared.