Why isn't there a limit to how many planes an airfield

Why isn't there a limit to how many planes on an airfield at a time? You obviously can't have like 100 planes at a little airstrip in the center of Brazil, yet its possible! Thre are limits on aircraft carriers, why not airfields? I would say like 5-10 aircraft for level 1 airfields/airports then 10-15, 15-20, 20-25, 25-50 and that should be the limit. Let me know what you guys think.