Should I use hypophora in my SOP? Hypophora is the question similar to question tag:

I want to shift the discipline from physics to biology. Why? Because, ...

Should I ask this kind of question in my SOP?

Function of Hypophora
The major purpose of using hypophora is to create curiosity among the
readers, while a well-timed silence produces heightened effects and
creates interest. It helps to capture the attention of the audience.
However, hypophora can also be employed to introduce new discussions
or topics of importance about which the readers might not have
information. Also, it can be used as a directional device to change
the topic. It can raise that type of questions which readers might
already have on their minds and would like to get answers to. In
addition, it is frequently used in political speeches as well as
literary works.

I don't think it will make any harm, but I'm not sure. Why? Because this comment makes me have to rethink of any, erm, nonstandard things.
I can't speak for all disciplines but in biomedical science this is generally considered an inefficient way of writing because the same sentence can be simplified to


  My reason(s) of shifting to biology from physics is(are)...


It's also considered tacky but I probably have to attribute that to overuse and misuse. I will only use hypophora if the statement is highly unusual or seemingly illogical. This is a bad use because the statement is not dramatic:


  To make tea I first need to bring the water to boiling. Why? Because...


Contrasting to:


  To make tea I first need to bring the water to boiling with a silver spoon in the kettle. Why? Because...


is probably synchronizing better with the readers' mental rhythm: "Huh? Why the heck would you put a silver spoon in it?" Then the following "Why?" would serve a better role: to resonate with the readers.

Surely enough in my own field nothing is dramatic enough for me to deploy this expression. Is "shifting from physics to biology" unusual enough to raise eyebrows? I am not sure without too much context. My gut sense is perhaps not because I'd categorize them both under the school of science and they do go together quite well. I'd think "shifting to biology after spending 10 years studying physics" or "shifting to biology from classical string performance study" may probably deserve a "Why?" Although, this is purely opinion.

The part after the "Because..." deserves attention as well. Make sure it's followed by a very compelling reason, or your "Why?" may be tainted with a taste of self-doubting or still-on-a-soul-searching instead of persuasion.

In any case, expressions like such are unlikely very harmful if used sparingly. They also serve to inject some liveliness into the statement. I'd consider using no more than once in a statement acceptable.