I cant fully agree with your statement in bold part, if there is no professionalism in gambling field then we will never heard some people who are well known as "poker pro".
I believe professionalism in gambling is exist, especially in games that is not pure luck based game like sportsbetting and poker.
I agree with you on poker, but disagree on sportsbetting. Indeed in poker if you always can quickly estimate your chances you win more frequently on average than those who can't. Another thing which can help to win is a well-thought-out bluff. But in sportsbetting: 1. You can't bluff; 2. If you are good in predicting which team will win based on previous results, then many others can do that too and basically you have to risk $100 in order to have a chance (although a strong one) to win $10. It reminds me of dice game when you bet with 90% win chance and get the 1.1x multiplier. CMIIW.