I am one of those people who still gamble using the demo when my funds for gambling have run out.
Playing using the demo mode does not mean that this is gambling but only for entertainment and using the demo mode can be used to find out the types of bets or set strategies before using real bets.
There is a clear difference between gambling with the demo version and gambling with money, even though in the demo version you are given a fake balance to bet with, it still does not give the utmost experience unless you are gambling just for the fun of it, but if you want to test your gambling skills or make some winnings.
Using the demo version won't give you exactly what you want or need, since in the long run, you have to walk away with nothing knowing you are in a demo mood and can't even make any significant progress in terms of skills and the rest of the what have you.