Bet that title has been used a million times.
Here”s how I have found them useful…
Hold my phone belt clip to the handlebars and the phone to the clip.
Mount a mini flashlight to the handlebars to be used as a headlight.
To hold my spare tube kit together.
In case it”s not obvious, you cut the tube cross ways to make rubber bands.
I carry extra in my repair kit and back pack.