Besides reducing the needs of using ledger lines and making the score easier to read, are there any other reasons?
There are two main reasons for this which have to do with the actual instrument ranges and what you can fit on manuscript paper. Different instruments play in much different ranges so having only one clef will make things difficult. Using the same clef for double bass and flute would be silly as you would have and instrument whose lowest note is C1 use the same clef as an instrument that can get up to D7.
As you increase ledger lines needed you also reduce what you can fit on an actual score especially when you have more than one instrument on a score. If we got rid of a clef then any instrument that uses that clef would pretty much take up an extra staff on a manuscript so you could not fit as much material per page.
The different clefs makes reading music easier. Sure everything could be written in treble clef, but counting 6+ ledger lines is pain especially when sight reading. The Bass clef and Tenor (also all other C clefs) make the notes fit into a staff and thus easier to read. It also shows the pitch relative to middle C, unless the clef is used for transposition. Example Bb Clarinet
It is not exactly clear, whether you are asking for a full score or a part.
For a part only one reason is missing from your enumeration, but this is in my opinion the most important one: convention or tradition.
You will have a hard time to find a viola piece notated in something else than alto clef, and even in case of success, you would likely receive a bewildered glance from a potential player.
For some instruments the conventions are regionally dependent, so French Horn seems to have bass and treble clef areas.