Why would you make a charge controller that is 30A solar and charge only 10 A load?

I have been wondering for the longest time.... Why would you make a charge controller that is 30A solar and charge. Only 10 A for load? I realize that the load does not have to go through the Controller but it is actually convenient and I love being able to see what my usage is as well. (speaking of the TrakMax30L) the charge controller is a well made controller as that is the only fault I can find with it. If it was 30A Solar/charge/load it would be so much better. My max load is 15A with every thing on in my RV, so I am planing to just add a second controller in parallel, to pick up the slack but it would have been nicer if I did not have to do that.