Why is it important to fit your persuasive appeal to your audiences interest.

So that you know what they care about and can use rhetorical strategies that will be effective

It is important to fit your persuasive appeal to your audience's interest because they will not bother to listen to you or consider your idea if it does not relate to them. In the context of the similarity heuristics, the appeal should be something relatable and 'similar' in terms of their interests.