i guess the closest i can come up with is that solo isn't really "solo" play if your effecting everyone else in elite with your actions, therefore its more of a "i'll keep the bad ppl away while you effect the powers" type of mode
a true solo mode would have its own universe on it, like the offline mode that was scrapped
this only makes any sense if you are also suggesting that everyone in solo and group mode are acting together in unison to cause an agreed effect on the background simulation.. is this what you think? in the simplest of terms, using PP as an example, the average distribution of player support per power is not a figure isolated to a single mode.. it will be present, concurrently, in every mode! players opt for the power that best suits them, based on things such as faction, personal gains, ethics or even morality.
the addition of other platforms adds to a better smoothing, or averaging of effect players have on the background simulation. so the more that play the game in its current 'all players matter' system, the more reliant the background simulation can become on player choices, and the less on FD's direction. conversely, reducing the amount of players that can effect the background simulation would actually create a need for FD to be more involved in the process of the simulation so as to avoid gross instability and unpredictability.
even if there was only a solo mode, unless a player could be on-line 24hrs a day, be present and persistent in every instance, within every system, it would impossible for that player, or even a group of players, to block the choices or actions of all other players involved in PP.