You have to be very good at it so that you can accurately predict the likelihood of a match outcome. It is not easy to have this skill.
Generally, successful bettors have a deep understanding of the sport they bet on combined with a disciplined approach to managing their money and their bets.

What I noticed about sports pickers is that they find exploit any discrepancies in the odds being offered by bookmakers. Making them really good at what they do and a bit of luck of course.