what are coins for?

aside from updating buildings at level 3 and sending out adventure hunters, what good is coin? i know its the default currency for loot spot buying too but, are people hoarding tons of coins to artificially increase the value? it looks to me like there are many ways to make coins but not many uses... not sure if i should continue to hoard coins...
i have about 1.5 million right now... on ares. what does everyone else have?

People like to keep their wealth in something and usually its kept in a resource most commonly recognized as currency. Here its coins..
I try to keep it in a resource that is always in demand on the market or is going to go up in value soon like adventures or currently beans/stalks so my coins are almost gone atm.