1 Some people are impatient
Some people are impatient and find it very hard to wait. Impatient people look for fast rewards and might lose motivation if they are forced to wait.
2 Their attention span became shorter
As the attention span of a person gets shorter, they find it hard to stay focused on one thing for a long period of time and they prefer to get done with things fast (See why our attention spans are getting shorter).
3 Technology has conditioned people to get fast rewards
Technology has conditioned people to get what they want fast. As a result, people got used to getting fast results and waiting became harder.
4 Life became fast-paced
Modern life became fast-paced that many people experience a sense of urgency. This sense of urgency created the urge of wanting things fast.
5 The internet taught people to find things fast
People who were brought up in the age of the internet learned to find things very fast online, and as a result, those people learned to hate waiting.
6 Humans are lazy by nature
Humans are lazy by nature. People always prefer the fast path over the long one.
7 They believe they have a limited time
People who believe they don't have enough time to achieve their goals always want to get things fast.
8 No long term vision
People who plan on the short term and forget the long term goals usually find it very hard to wait for results. A person who has a vision can work for years until they realize it (See how to develop a vision).
9 They have low tolerance
People who have low tolerance might find it hard to wait or to experience emotional uncertainty.