Nothing is "necessary". If you don't do it, and are happy, I guess the answer is obvious.
With the new events and different ways to make XP and Credits, is it really "necessary" to grind Indy still? Or is it just that alot of people want the "quickest" way to earn credits, therefore they grind Indy over and over still?
Just curious, not attacking here.
It is not possible to reach level 40 (A or B Spec) without redoing races.
It is not possible to buy every car in the game without redoing races.
Thus, "grinding" is necessary if you want to reach end game, or even to buy certain car's.
Sugar-coating the issue by saying "I was having so much fun, so I didn't notice" or "I just use different cars, so I don't get bored" doesn't change the facts.
If you want to progress, or even sample a fraction of the 40 Skylines available in Gran Turismo 5, you will be grinding. Prove me wrong.
I had to grind Aspec despite golding everything, to get to level 30. The seasonal events (not available at the time) would have negated my need to grind, but anyways my Aspec grinding was not bad enough to moan about. Bspec... now that is different.. be warned.In all honesty I have not found a great deal of need for unpleasant grinding unless my memory is truly failing me and I'm viewing the last few weeks through rose-tinted glasses.
Well, I golded every seasonal event. every special event and I am lvl 28 A-Spec. So I need to re-do Indy 500 two more times in order to be able to do Suzuka 1000km(lv29).
In B-Spec I need to re-do the Dream Car Champpionship 2 times to get to lv25. Everything else is done.
You could however try online. it will give you some A-spec xp, but at an alarmingly slow rate.
So yes, you will need to grind.
....
This game is about racing. If you don't race enough you won't see every content.