Why are there only 27 amendments

Why have only 27 Amendments been added to the Constitution? Because of Informal Amendments and how easy it is to informally amend it rather than formally. Why did the framers add an Amendments process to the Constitution? So it could change with society.

answer; ok in rural area most people depend on private transportation(cars),pick up truck,donkey and buggy: ),and urban people can walk or ride public transportation,bus,train cab,uber.

answer; longitudinal;