Why does the creature feel it is so important to come out of hiding and talk to the elder De Lacey?
In chapter 15 of Mary Shelley's Frankenstein, old man De Lacey is left alone in his cottage after Safie, Agatha, and Felix go for a long walk. De Lacey chooses to remain alone and, at that point, takes out his guitar and begins to sing very sad music. The creature, who has been observing the DeLaceys from a safe distance, is moved deeply by the music. This is when he develops the courage to enter the man's cottage.
“My heart beat quick; this was the hour and moment of trial which would decide my hopes or realise my fears. The servants were gone to a neighbouring fair. All was silent in and around the cottage; it was an excellent opportunity; yet, when I proceeded to execute my plan, my limbs failed me, and I sank to the ground. Again I rose; and, exerting all the firmness of which I was master, removed the planks which I had placed before my hovel to conceal my retreat. The fresh air revived me, and, with renewed determination, I approached the door of their cottage.
Let us remember that the old man DeLacey is blind, so he is completely unaware that the creature is, in fact, an abomination. The creature is well-spoken and delicate in its speech. It also identifies itself as a wandering traveller. This is how their conversation is, ultimately, possible.
We witness the extreme need for kindness and affection that the creature has. At one point the creature almost sounds desperate in his speech, strongly holds the hands of the old man and clings to his knees. This is when old man DeLacey asks the creature who he really is, and this is the exact moment when the rest of the family returns from the walk.
We know that disaster follows. Agatha faints, Felix drags his father away from the creature (who was still holding to his knees) and then attacks the creature with a stick until the it runs away.
Surely it is desperation what motivates the creature to take the risk of being seen. However, this shows how communication is a very important need for every living creature.