Why do you think that people's names are hard to remember?
Some researchers suggest that people's given names are the most difficult of all words to learn. Various theories have been proposed, one being that many of us have the same names. Common first names like "Mike" and surnames like "Jones" are more difficult to remember because, in our minds, one Mike Jones interferes with another.
The most popular theory is that names are meaningless - they do not divulge our appearance, our personalities or anything about us, except maybe a rough age, ethnicity, social class, etc. We do find it easier though to recall that a person is a potter i.e. makes pots, than if their surname is Potter.
A good way to remember names is to ensure you make a memorable association in our mind - this is probably why nicknames are better remembered.
So, you are not alone if you forget a name - it is perfectly normal!