I wouldn't go that far and say that it is gambling, there is a huge random factor in it but difference is you don't lose everything.
Gambling isn't Gheed anymore. It's using gold, crafting supplies, etc. to make crafted items with random mods. That's where luck will come in to play. But, casinos have been making piles of money for ages and people still enjoy them and people who don't enjoy them can stay home. So it sounds win-win to me!
Gambling is not only a fun way to spend your gold, it is also the best way in game to get certain types of items. It isnt supervaluable in terms of efficiency (high runes / hours) but it does offer you the option to quickly gain large amount of magic / rare items. I am a very gambling person and I really liked this option, it's a pity that it was removed. Personally, I have found an alternative for myself in the form of online casinos, many of them now offer excellent options, such as a 300% bonus when making a deposit, which cannot but attract. In any case, you need to play wisely, and only in this case you can win.