you could youse the same logic, to explain rings,,,,after all purse nets dont even need them.............
i think some people think sliders are faster than rings,,, in all honesty i dowt theres anything in it,,,,, just somthing difrent and personal choise..
oh and of course making a slider saves you 10p on a ring
you can make you own rings aswell drill a hole in a brush handel stick the end of the straining wire in and wrap the wire around the handel, cut and solder