On those peanut tanks those analog gauges are not necessary. Just a little arithmetic and a simple test to see how far a Sportster will go on a gallon of gas or whatever they are using these days. Real harleydoods will tell you they have another measuring device at hand.
The ones that are using the oil from McDonalds in their bikes? Nothin like a Harley that has loud pipes and smells like a French fry to attract attention.