Grandpa and Little Johnny are …

Grandpa and Little Johnny are sitting on a bench in the park.
Johnny asked, “Grandpa are you going to take that new Viagra?”
Grandpa looks at him and says “No Johnny, I will not.”
“But Grandpa, why?” asks Little Johnny. Grandpa replies.
“Because there is no sense in putting lead in your pencil if you have no one worth writing to.”