Because fearing the possibility that it could become chronic and further damage tissue cells? Or to lessen the pain and the amount of temporary ROM/function loss?
Probably a dumb question but I'd really like to know. As I understand it (not well. Ok actually just from a wikipedia article.) acute inflammation is the body response to promote healing process. Why not wait for some time first (how long?) and only then apply some ice if it doesn't get any better?