Your camera is going to get dirty.
No matter what kind of video you are making, dust, dirt and other things are going to get your camera dirty. The more these substances accumulate on your lens or sensor, the worst the quality of your image. Cleaning your lenses, and camera more generally, is something you must do regularly. Check out this tutorial on how to do it right from YouTuber Peter McKinnon:
A lot of people don't clean their gear properly, and even more people don't clean it at all. Don't be one of those people.