Transposing scores is the most logically consistent in my opinion. One big advantage is you can see the tessitura in a much clearer way, and in my experience glean a little more insight into the mind of the players. However, as others have often stated, concert pitch (C scores) are simpler to read. The reality is they are actually transposing.
Octave transposition are considered equivalents (and yes people have argued over this) so as some orchestration books point out Bass, Guitar, Contrabass and a whole bunch of others instruments are simply notated at C and sound an octave up or below written.
A common classroom observation about transposing scores: “if a player sees a Middle C written on the page then they should play a Middle C. No? The current way seems bloody daft to me… ” Is actually a good one. Seems so simple right ? I am sure many people have suggestions for reforms. To have a basic understanding of why things are the way they are you need to dig through the history books.
For a long time vocal music was the main form of musical composition. Of course men and women have differing vocal ranges. The staff was designed to cover the most essential parts of a persons range (about an 11th from space below to space above). In order to keep most of the notes on the stave, each voice had its own clef. This was still pretty common until about 250 (+or- 25) years ago. Bach did not notate his chorales like we study them in University today. You can google “Open Score” to find examples. You will notice a logic more like you are suggesting. The difference is that a harmonization was preferred to a unison doubling as you ask. Think about it: if you have a C in treble the same placement will become a E in Bass clef. For composers of the past who were fluent in these clefs they could take a line (say ascending major scale) and if treble and soprano was used, marking in the exact same spot a harmonization in thirds would result. (C, and A).
There are other reasons too. Horns did not have valves, and certain other instruments had to be set at various pitches for reasons of instrumental construction. It’s a topic in and of itself. Oh, and toss in the absence of equal temperament.
Last thing: I must say I was pretty surprised to find out how useful it was to learn to read in the other clefs. I studied with some pupils of Nadia Boulanger and they made me learn them all !! (Soprano, Etc.) It really helps with reading transposed scores. If I am reading a Bb clarinet or trumpet, all I have to do is think in tenor clef. It really is not that taxing. And it is great for practicing transposing at the keyboard