I didn't know drinking out of canning jars was a thing people were doing (except for moonshine, for obvious reasons of authenticity), but I suppose it makes sense. At very least, you don't have to worry about leaking issues. However, while drinking out of jars works exceptionally well while seated and motionless, the process is less smooth while walking. So, someone invented a sippy-cup lid for jars. America is awesome, right?