Why don't pennies and nickels have ridges on their sides?

I know quarters and dimes do, but why not pennies and nickels?Why don't pennies and nickels have ridges on their sides?
It goes way back to the days when coins were actually made of gold and silver. The reason coins have reeded edges is so if someone clipped off a little of the gold or silver it would show. Even the first cents and 1/2 cents had either a lettered edge or denticles. Our early silver dollars had lettered edges some what like the presidential dollars of today. Back in the days of English hammered silver pennies someone came up with the long cross penny. The cross went to the edges of the coin, if metal was shaved it would show. When the U.S adopted the small cent and nickel they felt there was no need to add reeding due to their low value and not being made of gold or silver. Hope this answers your question.Why don't pennies and nickels have ridges on their sides?
Probably so blind people can tell the coins apart