For the same reason
> If a person puts such a question to you as: ‘I have divided ten into two parts, and multiplying one of these by the other the result was twenty-one;’ then you know that one of the parts is thing and the other is ten minus thing.
is inferior to
> x(10-x)=21
The succinctness helps your brain focus on the important information so you don't get lost in the noise. If you find it hard to read at first, your brain can adapt to the patterns just fine.