Why I personally don't enjoy playing in demo mode, or in other words "for free", is because you have no chance of winning anything playing like that. There are slots which propose you like 50,000x or even 100,000x potential multiplier, and if your bet is just 10 cents you can potentially win thousands of USD. And that's what makes gambling exciting. Playing in demo mode you just delete that excitement.
Same here, I consider it waste of time since you can’t gain anything by doing that while most of the slot games is boring if played in demo. Winning money is what makes slot games intense and fun.
Most importantly, You might hit max win on demo which is just a shame to the opportunity like that while you can use small amount on bets to risk small to have a potential huge win.
I manage to win a max win on San Quentin slot games but on demo mode. After that, I never play demo and always bet the minimum when doing relax slot game play just in case I manage to hit max win again.
San Quentin's max win is 150,000x. I mean, even if your bet is just $0.10 you win $15k. No one in the world would mind winning that amount. Even Mark Zuckerberg wouldn't.
I can't say I have quit playing demos. I find it entertaining sometimes. But the funny bit is my real winnings are actually much bigger than those in demo mode.