Math textbooks for undergraduate and graduate students are almost always structured in the same way. Each chapter/section/etc. has it's definitions, theorems, propositions, etc. with proofs following the statements directly.
If we now take a look at, for example, a physics text book, we will probably find a completely different approach in the structure. Instead of building blocks (theorems, etc.) we will find a continuous text, where the problem is usually introduced in the beginning, some calculations and reasoning done in the middle part with the result at the end of the chapter/section/etc. Instead of physics we could have taken almost any other field, I at least don't recall seeing such a strict way of dividing a book in building block as it is done in mathematics in any other field, and found the same result.
Of course there are some exceptions, at least in physics one can find books that are almost math-like in structure (often called Some-field-in-physics for mathematicians), but generally speaking this separation in theorems/etc., or more generally in such building blocks, seems to be something almost exclusive to mathematics.
And now to the question: Why do we have such a strict separation in math textbooks? What are advantages and what are disadvantages? Do you know some examples of textbooks outside of mathematics that have attempted a similar structure?
Honestly, I always preferred the approach that math textbooks had over that of other disciplines (mostly physics, not really familiar with the rest). There are obviously some problems when it comes to the math-approach, like f.e. steps that are not motivated enough, etc. but the fact that I am able to see the thing that we are going to prove on the next few pages in form of a concrete statement (theorem, etc.) helped me to not lose sight of what we are actually trying to do. On the other hand in physics you often start with something and have no clue where exactly you want to go/what you want to show (well, the lecturer/author/etc. knows but the student/reader has usually no idea)... So I was wondering is there a reason why such an approach is usually avoided in physics?
Notes: This question was originally asked on PhysicsSE (see here) but put on-hold for not being on topic. I therefore re-framed it a bit in the hope to make it on-topic for this site. I hope the structure of math textbooks is also part of math education... If not, please feel free to suggest a better site to ask this question.