Some users will change the default store path while downloading. Therefore the free space on your C drive will decrease little by little, which may cause slow performance of your PC and your games may often get stuck.
That's why when you download programs, those you downloaded will be automatically saved on the C drive. When you download and install a program from a website or platform, the Downloads folder is the default storage location that is used to store the files or programs. Can you move installed software to another drive?