The junk boxes are balanced to hold the amount they do so they don't become too powerful a way to make money. This is done with most ways of making money, so asking them to change without providing a good reason why is useless.
This is very true, and this is also why I am on the fence about bumping up the slots. I feel it would cause imbalance if I were to bump it up. I have been thinking about bringing it up from 20 to 30, but I am still thinking about it.