Risk management is at the core of both investment and gambling. The riskier your investment, the closer it comes to just putting the money on a roulette position in practice. There are plenty of portfolios that slowly hemorrhage money and/or eat up any would-be growth via fees: those are your 51-49 splits. Also it doesn’t matter if there’s such a split if you decide to go all in and it goes belly up, however you slice that.
If you do risky shit with money, it’s a gamble whether it pays off. Maybe I’m misunderstanding the point you’re trying to make?
The problem, like with many things in life, is that there’s a desire for people to place clear delineations on things for purpose of clarity and peace of mind, when it actually exists on a very fuzzy spectrum. I’d argue you do gamble a tiny percent chance of getting in a wreck every time you drive in exchange for getting places much faster. Likewise, were you to walk instead, there are unique risks and payoffs associated with that choice too.
Whether or not the risks are well known or there’s a decision to increase the level of risk is a little beside the point. There are plenty of people addicted to gambling who genuinely believe they’ll hit it big and retire one day, and that the reward payout is inevitable even when it’s clearly not.