Commercial value of RP

[JC Lawrence]

Something that just struck me is that all the commercial
representatives we have on the list seem to espouse their games as
being RP games, and discuss their values in terms of the RP values
generated by their games.

Is this valid in a commercial sense?  What are its origins?

Are the commercial games marketed and defined as RP-centric because
that is what the general market demand is for?  Because that segment
of the market that might be or is interested in MUDs demands RP?
Because the game playing populace equates MUD worlds with RP?  Because
of the greater competition levels from the non-RP DOOM-esqe games?
Because RP is considered synonymous with MUDs when selling the concept
to the commercial vendors?  Because the main activists in the
commercial MUD ventures personally value RP highly and thus have a
high personal interest in creating RP games as versus non-RP?

Or, more commercially, are the games RP-centric to encourage longer
connect times and thus greater billing possibilities such as
ancilliary profit sources from advertising (more opportunities to
deliver an advertising message to a player due to the longer connect
time)?  

I sense some sort of unrealised synergy here.