Right, but you should only give them money if the product that they have on Early Access is already fun, right?
Take Rust (the game, not the language) for instance. They cobbled together what is now known as "Rust Legacy" as a sort of demo of what they wanted the game to be. Thousands of people bought it. Now Facepunch is using the funds from all those sales to completely rework the game from the ground-up. Now it's better than Rust Legacy, and only going to get better and more interesting.
But if Rust Legacy wasn't fun, nobody would've bought it. TL;DR: don't preorder (including early access!) games purely on promise alone.
What if what they have so far isn't fun, but you think it might become very fun if they were given enough money to finish it? Isn't that (sometimes) worth taking the risk on?
To steal an idea from Bungie, when it comes to games you want "thirty seconds of fun" -- a base gameplay loop (in the case of Halo, where it originally applied, it's the loop of taking out baddies from a distance, then the stronger baddies from mid-range, then mopping up the scattered weak baddies). An early demo (like the aforementioned Rust Legacy) is a proof-of-concept of that base gameplay loop, and if players like it, they can fund it.
Once it's funded, they can build out from that base loop, and eventually you'll get a finished product.
Take Rust (the game, not the language) for instance. They cobbled together what is now known as "Rust Legacy" as a sort of demo of what they wanted the game to be. Thousands of people bought it. Now Facepunch is using the funds from all those sales to completely rework the game from the ground-up. Now it's better than Rust Legacy, and only going to get better and more interesting.
But if Rust Legacy wasn't fun, nobody would've bought it. TL;DR: don't preorder (including early access!) games purely on promise alone.