People who buy diamonds, physical diamonds, may be speculating on them. Others may actually like the diamond. For whatever reason, they bought the diamond, and now own it, and can resell it. It isn't illegal to buy something in the hope it goes up in value. People do that all the time with videogames, cars, whatever.
Now, let's say ownership of a diamond was moved to the the blockchain. Not only could you buy and transfer it easily, provably, securely - you could even buy 0.000000001 diamonds, or 100000 diamonds, just as easily.
In my opinion, all of this is objectively better than kickstarter.
Sure, because you don't even have the little bit of oversight that kickstarter offers. In your case you can just keep pumping coins into the market while they have any meaningful amount of value. Then when they are worthless you just claim your project failed and take the money from selling the coins.
a) the token is redeemable, and in that case why buy securities you don't intended to use (speculation is the only reason) b) or the company folds before delivering and the token is worthless, so by selling it you are just pushing the loss to a greater fool
Either way, this is objectively worse than Kickstarter.