That's a twisted logic if ever I saw one.
The demo is how it is, and it's SO much more than you've paid for. If you want more from it than you're getting, buy it.
The demo received much of the improvements that S2 got. Tyres are great now, and aero is too. So you don't have the BF1. Boohoo.
The game already justifies the spending of the money. I should know because I DID spend the money. When you spend the money too, you can tell other folks if LFS is worth spending the money just like me. Until then, you can't justify anything except telling people whether you think the Demo is worth downloading or not. Now THAT is logic.