Considering this is English, I'll assume these are text based questions, in which case a book title and chapter reference would be needed to accurately answer this question. But, my guess is that the Capitol did not care to clean the arena, or made special effort to keep everything in order. In the first case, that would say that the Capitol may be poorer, and be understaffed and funded, or that they are simply hapless. The latter, would mean that the games are very important, as well as they Capitol having the money, time, and man-power to keep the arena in order. The Arena could be an iconic place and detrimental to the public relations of the Capitol.
