1. To get higher rates of return, you expose yourself to more risk of losses. The risk is real, i.e., you could lose everything.
2. You need even better (riskier) returns to pay for all the legal/investment/accounting advice because lottery winners rarely have experience here, at least not in the first year.
3. You need even better returns (and more risk) to make up for the taxes you pay up front. The annuity is based on pre-tax funds, and federal tax is much higher than the 25% initial withholding.
4. A $2-3 million windfall is more than enough to live on a sensible six-figure budget and get some practice with investing. If you screw up, you get another windfall next year. Just avoid debt.
5. Will taxes go up in 10 years? Who cares. They won't go to 100%. Even if you lose everything for 9 years straight, you'll still be rich in 10 years with far more certainty than if you took the lump sum. Just stay out of debt.