It is not expressly a mechanism of punishment. It is expressly a mechanism of debt repayment; it can be argued that that is closer to a mechanism of forgiveness than one of punishment.
Sort of the other way around; 3s are 4-door by default, and 4s are two-door by default. They still make 4-door coupes (following the technical definition of a coupe, rather than the popular definition) in the 4 series, namely the GC.