When you can't even see a part, you might forget about it, but it doesn't mean its not important. Flat tires are probably the most common bicycle failures. Many times, flats are caused by the rims, specifically the lack of protection from the rims' sharp edges. Good rim strips didn't exist for BMX rims. They work well and improve the function of any 20 inch rim. If you forget about them, that means they are doing their job.