Answer:
The answer to this question is that polls are a way to inform, teach, and even sway, people´s opinions, views, and learning, on different topics. So, the purpose of it should be to obtain the maximum accuracy possible in its results, which means that a scientific poll will follow the necessary process and procedures to achieve this goal, and give accuracy. Informal polls can generalize information without any real backing, and cause problems.
For example, a poll wishes to know the intention of voters for one party, or the other, for a candidate, or the other. So the foll might ask how valuable to a certain topic is the input of each candidate. In a scientific poll, researchers will follow the necessary process to ensure sample data is accurate, measures are accurate, and results are accurate, to give people an accurate, objective, centered answer to the question.
In the other type of poll, the informal, the results might become dependent, totally subjective, and may sway people the wrong way without having actual, and accurate backup. So in the example, people will refrain from voting for one of the two candidates because the poll wrongly, and inaccurately, reported a view from the candidate that was not the correct one.
This is why polls are better to be scientific, rather than informal.