I think the amount of "respect" that gets attributed to a degree isn't really based on what the actual content of the degree is. It's very difficult to say that one subject is objectively "better" than another, in most cases. Rather, respect and prestige are awarded based on how competitive it is to get onto that degree, and the standards of talent that an admissions tutor for that subject is going to require. If a certain subject only has tends to have entry standards of BCC, and a different subject has standards of A*A*A, naturally people will be more impressed when you tell them that you successfully got a place on the latter degree course, regardless of what the actual subjects are. Some degrees are only accessible to amazing students - and that's ultimately what you're being respected for.
Science subjects tend to carry more weight in the jobs market, especially when looking at the higher paid jobs, and so it makes them quite attractive to students who are capable of getting onto them. (Though there are exceptions - a Law degree is probably going to be more "respected" than a Food Sciences degree). Places on the corresponding degrees become more competitive, and the entry standards go up, and they're more respected as a result.
Of course there are attractive, competitive and lucrative professions in the Arts as well. You'd have to be outstanding to bring out a best-selling Music album for example, and would probably be awarded a lot of prestige for successfully achieving this. But this doesn't confer the same respect onto a Music degree, because a degree is not necessary to excel in this career. Neither Michael Jackson nor Mozart had university degrees in Music. This means that degree places aren't quite so competitive, neither are they as prestigious, because a person wouldn't need to be as outstanding in their field to successfully get a place on it and complete it.