If you've got a million dollars and put it into an index fund you'll make ~$100k/year. If you day trade and make "Decent money" of say $70k/year you're still at a loss vs if you took the less 'risky' approach. Even if you made $150k (50% over the index) it's still a loss due to lost opportunity cost. As the $100k index + a job at McDonalds making $30k/year still puts you ahead due to long term vs short term capital taxes. And if you've got the knowledge to day trade and earn more than 50% over an index you can probably command a better job than fast food.
If you don't have a million in capital it becomes harder and harder the less money you have.
Your friends would need to consistently beat the market by a percentage of their capital for it to be considered a 'win' imo.