Was looking around in my puter and found that system restore is disabled. No idea how, why or when this happened. Does anyone know a reason why I shouldn't turn back on system restore?

*edited to add*
I have a couple system restore points that I have set myself. Last week I tried to use system restore to fix my puter by using one of these points. It told me that it could not restore my puter to this point. Does anyone know a reason it would refuse to restore my puter.