Because the use of "that" and "same...as" are two different grammatical constructions. (a) I applied for the same company that my brother did. Here "that" introduces a restrictive clause. I applied for the same company as my brother did. (b) Here, the combination "same...as" is used to say that two things are equal in some way. The above two grammatical structures are different. But (a) only looks similar to (b). And (a) does not have to have the word "same." So, we could have (c) I applied for a different company ____ my brother did. Which one do you think is correct here? Think: if you use "that" you are making a restrictive clause "that my brother did." If you try to use "as," you are trying to say two things are equal in some way. Again, you can have: (1) She thinks the same as I do. Reason: "same...as" = two things are equal in some way But you cannot say: (2) *She thinks the same that I do. This is incorrect grammar. But you can say: (3) She thinks the same things that I do. Here, "that" introduces a restrictive clause.

"as" is used in the first sentence because it means that we are comparing between " the style of the clothes that the clothing manufactures make" and " the style of the creations modeled on the runways of top European fashion houses " but in the sentence " I applied for the same company *that* my brother did" it means that there is one company that me and my brother applied to it ..