Why do acids have low pHs and alkaline solutions have high pHs?

The pH scale is a measure of how many H⁺ ions there are in a solution. The higher the concentration of H⁺, the lower the pH and the more acidic the solution is. For example, for HCl, dissociation can occur such that we get H⁺ and Cl^- ions in the solution so the pH is low and the solution is acidic. For NaOH, dissociation results in Na⁺ and OH^- ions and as the H⁺ concentration is low, the pH is high and the solution is alkaline.