Resale price maintenance.
wFree-rider externality.
nFor complex (or new) products requiring information services or customer support, manufacturers want to provide a bundled good: product plus info and/or services. 
nCould integrate vertically into distribution, but that may be costly if there are diseconomies of management or scope.
nBy preventing price competition, RPM forces competition among dealers onto other margins, notably point-of-sale­services.
Alternative hypotheses.
Discussion question: What then is the rationale for maximum RPM?