I could not agree more with you mate. Gambling can just be one of the many places we can spend some of our money to be entertain and have fun and not necessarily make gambling as our main source of income.
Only a very few people are gambling just to be entertained and have some fun with their money. When you say that it is not necessary to make gambling as major source of income, you have to think about it again. There are so many gamblers struggling with this argument, they are supporting themselves for being a full time gambler because it is their own source of income as they are earning good with it.
A lot of people aim to become gambling as a source of income but unfortunately majority of them failed, that is because they don't have the skills or they don't play the right game where they can use their skills. There are two types of gambling which are the skilled based and luck based games, if you want a long term success you should focus on skilled based games but you need to develop yourself to improve because knowing the game alone does not guarantee a win.