While it's probably true that many gamblers like to increase their betting sizes with their winnings they make. I also think that there are is a large fraction of gamblers that are more disciplined and save some of their winnings. At least for me and most of my friends that like to place bets on sport games, we have a group bet on big tournaments where everybody puts in 10 USD. We have been doing this for a long time and when we win, we still keep betting only the initial 10 USD and have a few beers with the winnings. To me the 90% of people losing seems like a way to high number. There must be many more people that only bet on large tournaments and focus on save bets, where the chance of losing is fairly small. And like you said people that only are using sports bets to make money, will take out winnings to invest them in other things too, for long term profits outside of gambling.
Some people do increase the betting on the same game and it leads to huge loss.It's essential one to save some money for the future gambling.The should have an disciplined game with certain interval on the game.So they won't loss the hope to get back the loss money.The potential to recover the loss money from the same gambling will be the character of the experienced gamblers.As like trading of cryptocurrency with the ten dollars,many gambling games was their below five dollars to ten dollars.The only difference is the winning money from the low bet will be lower as compared to the winnings of the high bets.