I started writing, or rather, thinking, stories as a child, and at that time the reason was very clear.
Whatever I'm reading at the moment seems to influence whatever I'm writing.
SF has at least the advantage of not depending on preconceptions.
This is mainly because I spend a lot of time writing and so don't have much time to read; I hate to waste that time reading what may turn out to be junk food for the mind, when there's so much real writing to be read.
People have laughed at all great inventors and discoverers.
The future, according to some scientists, will be exactly like the past, only more expensive.