Re: "But your comment about tenor clef being easier for cellos because they`re experienced (and it holds true equally for bassoons, and probably trombones) makes you think - how did they get experienced in reading tenor clef, and surely treble clef would have been easier when they started! I know it would have been for me, as I had a piano background."

ONLY because you have a piano background. For most cellists the treble clef is more difficult than the tenor clef (and always was) because most cellists learn the tenor clef first.

The tenor clef is difficult for me because long before I took up the cello (as an adult and fairly recently) I had been in the habit of transposing tenor clef bits in orchestral scores by pretending they were treble clef bits and then going a ninth down. The habit was and remains thoroughly ingrained, and it slows me down in fast passages. In any case, I was amused to see that someone had written letter names above the few treble clef notes in my cello part in the Romeo and Juliet Overture I was recently performing with my amateur orchestra while leaving the many tenor clef notes alone.

Re: "We also use Tenor clef as a transition between Bass and Treble clef because it is much easier to use 3 clefs and have the notes stay in relatively the same position on the staff than to be reading at the top of the staff in Bass clef and suddenly have to jump to the bottom of the staff in Treble clef."

That sort of thing is not uncommon in piano music. Somehow pianists survive it.

Re: "Bass and Treble would not work to be the only clefs used for us. The use of Tenor and Treble clefs for the cello at least is to avoid ledger lines because too many ledger lines slows the ability to play the notes as quickly as needed."

In the nineteenth century treble clef cello passages were read an octave lower than notated, obviating the need for the tenor clef. In the Romeo and Juliet score the same tenor clef passages to which I referred above are written in treble clef an octave higher. Various orchestration texts complain about this practice, but that`s only because the "obviating the need for the tenor clef" thing eluded them. Where the cello goes above this transposed treble clef a simple "8va" will suffice, but that only commonly happens in cello concertos. Orchestral cello parts rarely go above the second D from middle C and usually restrict themselves to the A below (A440).

On the pieces of cello music that has treble clef, can you imagine that all the music in the cello clef instead of some of in in also treble clef. There would be a few lines per page

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Re: "On the pieces of cello music that has [sic] treble clef, can you imagine that all the music in the cello clef instead of some of in in also treble clef. There would be a few lines per page"

In the first place, I can`t tell what you mean by "the cello clef". The alto clef is sometimes called "the viola clef", and although this is not a legitimate or proper term, it is nevertheless clear, but only because there is no modern instrument other than the viola that currently uses the alto clef. This is not the case with any of the three clefs the cello uses. The bass and treble clefs are used by far too many instruments to list here, and the tenor clef is used by the double bass, the trombone, and the bassoon as well as by the cello.

You appear to be complaining about leger lines, but, in the second place, my posting above already explains why discarding the tenor clef would not necessarily result in excessive leger lines. The original Romeo and Juliet SCORE (in contradistinction to our modern extracted parts) does not put the cellos in tenor clef ever.