Imagine this, you are trying to win $500 with $20 balance so now that seems pretty unlikely but with the clan feature its kinda likely. Imagine having 10 people pool in $20 each so that would be $200 in balances and its way easier to get it to $500 rather than trying with your $20 alone. This is pretty much the function of the clan feature, bigger balances to play together with another player
That's best thing for small gambler to pool the funds and have a chance of winning some big amounts which are not easy to attain as an individual gambler and in clan you gamble like a group and it also increase healthy competition among clan members also.As you said there are more chances of getting high multiplier with big wagers and clan money help you out in this manner and will see how much the players like this feature.