I have often tried contacting relatives or potential relatives, and each case is different.
One reason could be language, and I have a story to tell concerning this.
Possibly, my most disappointing case was when, a few decades ago before the days of Google translate, someone tried contacting my through MyHeritage in German and although I responded in English saying that I did not understand his message he never replied to this. Eventually, I revisited this message (with Google translate), and it was from the son of the husband (will call this husband "great-uncle" although am not biologically related to him) of my great-aunt, through his first marriage. Actually, after my great-aunt passed away, I and also my parents z"l (who lived in England) became relatively close to this great-uncle and when I visited England, he would often treat my brother and I for a meal at Blooms (kosher restaurant in NW London). He had asked me to try and search out any relatives of his, but he wasn't specific.
It is true that most people are not interested in their roots, and in general, they do not want to be bothered if it is not family they know. I did manage to find a third cousin who is happy to stay in contact with me socially but has a hard time with accepting we are cousins because all the evidence comes from the "paper trail", and he trusts this less than I do. Neither of our families on the mutual ancestry talked about their family.
Ma'aleh Adumim, Israel