there is a certain wish about official factions to act as examples in a positive way indeed. - however... it is a guideline because official factions have structure.
it does not mean that an individual player may not act in the same way - execute the same influence on the storyline. - as a matter of fact, it is very much wished for EVERY player to act according to highest standards - not just official factions.
keep in mind....
when the official faction was created - there must have been a reason to join. - if the reason was to apply a higher level or roleplay ( subjective ) - such a reason should not have vanished. - if your "good" example shows no effect on others ( as it did on you, when you joined an official faction ) you either have to try harder or realize that your way is not what attracts other players ( see what i wrote about like minded players )
in the past - official factions and unofficial factions or individuals have affected the storyline, lore and roleplay alike. we devs focus on official factions mostly, cause it is easier - for an individual to make a similarly great impact, he has to work much harder to be noticed - but lets face it... even if its an official faction behind change - it really usually is very few players, sometimes a single player anyway ( no matter if he wears a tag or not )
but by pointing that out, you already presented a positive incentive to join a faction other than restrict others. - since official factions are easier to monitor in a good way - a player with a great vision has an easier time to make it become reality. - if he is surrounded by "like-minded" players, he may even find instant backup.
anyway .- what i wrote applies to "why you joined a faction"
i daresay - most players don t join, cause they want to be an example for others. - thats rather ooRP for an inRP game - and its also a bit rich sometimes.
most players really do want to join cause they want to feel like being part of a group ( or the head of a pack, you never know with some )