Why "a judgment of taste cannot be based on a subjective purpose?"

In section 11, Kant wrote in the beginning:

Whenever a purpose is regarded as the basis of a liking, it always carries with it an interest, as the basis that determines the judgment about the object of the pleasure. Hence a judgment of taste cannot be based on a subjective purpose.

I don't quite understand why the the statement of the second sentence is true, and I don't see the connection between the first and the second sentences.

And, I also noticed something interesting in the last sentence (§11):

Therefore the liking that, without a concept, ...... , can be nothing but the subjective purposiveness in the presentation of an object, without any purpose (whether objective or subjective), and hence the mere form of purposiveness, insofar as we are conscious of it, in the presentation by which an object is given us.



(編輯記錄)

"Whenever a purpose is regarded as the basis of a liking" means if an object is liked under the condition that it can lead to some result (which is the target of the liking). Such a liking is hence a liking based upon and determined by an interest. Since the liking for the beautiful has been divided from the other two in the previous treatise, and since the disinterestedness nature of a judgment of taste has been assured first, with the same reason supporting the two "since"s, Kant writes "Hence a judgment of taste cannot be based on a subjective purpose. He does not mention objective purpose because it is too distant to be a question.

Ya. I have thought about it after posting the question and somehow got the point. It's like a stupid question...