Disregarding a demand letter can cost far more money than a consultation with an attorney, and you need to decide if the gain from that choice is worth the cost, hence the need for a consultation.

(Though its less likely, complying with such a letter can also have hidden costs, so a consultation may be a good idea even if that is your inclination, but you are usually far more likely to experience adverse consequences beyond those you voluntarily and knowingly undertake from disregarding than from complying wiht such a letter.)