1) So what lottery odds are not allowed?
2) Can you name a single lottery with odds in your favor?
Cause with cryptocurrencies, so far, the investors have made money on average.
2.) There's been multiple cases where lotteries were -accidentally- setup such that the odds were in the favor of players if they pursued the right strategy. Here's one: https://www.theatlantic.com/business/archive/2016/02/how-mit...
A history of gains to investors aren't an definite indicatio that an investment is good, or that the overall odds favor the investor. If I go into a casino and win roulette 3 times in a row, that doesn't mean the wheel is biased in my favor. Similarly, in most ponzi schemes, all of the early investors make money.
(And even in a non-fraudulent situation, simply having an investment go up doesn't mean it was a good investment, when examined on a risk-adjusted basis vs. other alternate options.)
The problem with back-end enforcement (and those laws do exist) is that it doesn't remove the incentive to try issuing a scam-ish security and hope you will evade prosecution, and the damage done can take years to unwind, if it's even possible at all. This is why there are regulations on public offerings of securities to non-accredited investors.