In addition to gambling "for luck", there are those in which certain knowledge is required. And first of all these include sports betting and poker. There are those who and in such games I play blind, like roulette. But most play them based on their knowledge.
Even in skill-based gambling such as poker or sports betting it's not as simple as having some skills and making money. It's a
competitive job where you have to be
better than many (or most) of other people trying to do the same. Not like for example being a truck driver or a plumber, where you just need reasonable skills and willingness to work hard.
It's somewhat like the situation in those sports that gamblers are betting on. For every successful professional basketball player there are thousands of kids whose parents spent a lot of money but it didn't result in a professional career. They maybe got other benefits out of it (health/exercise/enjoyment) but if their goal was to make money then they failed. For every successful sports gambler there are many others who have to lose in order for the few to make money, and for the bookmakers to make money.
If someone takes up poker or sports betting expecting to make money they're almost as likely to be very disappointed as if they were playing dice. They do have a slightly higher chance in skill-based gambling, but they have to be extremely good at it to make use of that small opportunity.