I am sorry, but in this day and age you can't really claim you were not privy to the contents of the game at launch; especially in the case of driving games, you know very well what you're paying for (if you have kept up to date, of course). T10 and PDI haven't made false promises about the content of their games, indicating that they would've featured more cars, tracks or gamemodes than those found "on disk" (or, in T10's case, being very clear they would't have been available at launch). Neither have they deliberatedly locked on disk content behind a paywall. Both are things that happened recently in the history of gaming - the No Man Sky and Mass Effect 3 D1 DLC fiascos come to mind.
And as for the usual accusations of developers holding back content that was ready on day one to release it piecemeal later on, keep in mind that a) the developers are free to consider that the overall value of the initial game and additional content exceeds the retail price for a game (which is 70€, give or take)(1), and b) the delay of the April content update would seem to prove that, at least in the case of T10, that is simply not the case and additional content is finalized post-launch.
And if you're going to say that "yeah, but the content FM7 or GT Sport offered at launch isn't worth the ticket price to me", well, you're free to think that. But it's an individual opinion based on your expectations and the value you give to your money, not some objective reality. The truth is, there is no metric to what a "full game" is other than "people are willing to pay the price of a full game for it". And after all, we live in an age in which no matter how much content the developers will put in their games, there will always be someone complaining about the price.
(1) in the past, this would've resulted in that additional content not being developed at all. Game development is a business, and as all businesses, it operates under the assumption that investments will generate a financial return