Why is an inelastic demand curve "insensitive?" Provide an example of a good or service that fits the description

If the amount demanded of a commodity declines significantly due to a slight change in the price, it is said to have an elastic demand. This is demonstrated by goods that are sold in perfect markets. On the other hand, a good whose demand remains relatively constant despite changes in the price level has an inelastic demand curve. Since elasticity looks at sensitivity, these goods are said to have an insensitive demand curve, usually represented by a vertical line. Prescription drugs such as medication for diabetes and necessity products such as groceries are examples of goods with insensitive demand curves. These are products that individuals cannot do without or whose consumption cannot be postponed.