Sherlock Holmes actually uses abductive reasoning, not deduction. Abductive logic is actually a thing, and has been since the 19th century. Abductive logic allows for leaps in judgement when missing gaps in knowledge / information are present. It usually requires that the reasoner be a person with greater analytical skills than the average person, which is why it is not as popular as induction, deduction, or lateral reasoning. But it does make for good stories, hence Sherlock.

So, why did Sherlock called his method deductive if it was actually abductive?

In Arthur Conan Doyle's time, abductive reasoning was a relatively new method in informal logic, developed by Charles Sanders Peirce. At the time, it didn't have much of a theory behind it, so it was considered to be a sub-branch of deductive reasoning which was made popular by the new criminology techniques of Scotland Yard which inspired the creation of Sherlock. It wasn't until much later that a distinction was made between deductive and abductive reasoning.

I think for the most part, people are typically abductive reasoners, even when they aren't trying to be. Our instinct is to try to guess our way out of a problem whenever we can't find a logical solution for it. They will try to subvert the logic by thinking out of the box. The problem with this is if you don't start from a place of logic to begin with, the abductive reasoning quickly degenerates into irrationality.