organic chemistry - Nomenclature of Halogen substituted Alcohol and longest chain

For the following compound, the correct IUPAC Name is "4-Chloro-3-ethyl-2-(1-methylethyl)-butan-1-ol" but according to what I know, Chlorine is a substitutent and alcohol is a functional group. So including alcohol is necessary but not $\ce{Cl}$. And if we see the longest chain including alcohol then it would be a pentanol rather than a butanol. Why are we not naming it like that? Is it because the substitute $\ce{Cl}$ is necessary to include? Or what?