I believe that repeat signs have a very useful function in musical notation.
For example, when scoring a J-pop song, if the B-melody and chorus parts are skipped to the A-melody and first chorus using repeat signs, there is no need to write the same score again.
Repeats are very common in classical music scores. For example, in Mozart’s “Turkish March,” if you follow the repeats exactly, you would have to play almost two pieces of music. However, these repeats can actually be omitted.
The reason why repeat symbols were so frequently used in the Baroque and Classical periods is that the performance was basically a one-time-only performance by the composer at a time when recording media, which is commonplace today, did not exist. The sonata form is a prime example of this, and the repetition of the first theme in the recapitulation section has the effect of strongly appealing to the listener’s mind.
On the other hand, it is not at all unusual to omit repeats in today’s concerts. In competitions, repeat signs lose their function for the purpose of reducing the time per player or for the pianist’s or conductor’s own interpretation. For beginning piano students, we would like them to practice without omitting the repeat signs, because we want them to value “playing according to the score,” but at concerts and competitions, they may choose not to repeat in some cases, after consulting with their instructor!