I understand all about transposing instruments. However, my question is why not label the keys of these instruments such that when you play a particular key (say "C") it sounds like a "C"? This idea of it sounding like some other key is totally unnatural. Yes, I get it that if you switch between different transposing instruments that you maybe want the same fingering........or do you??? This is keeping me from taking up the alto flute as playing the piano for decades I'm used to reading, playing, and hearing the note that is on the sheet music. To do otherwise is totally unnatural to me. So in my case why not just label the normal "F" key on the alto flute to be the "C" key. That way the confusion is gone and everything is back to being like a piano. No, I have no intentions of ever taking up another instrument so why shouldn't I start off learning the alto flute keys like described above??
It's good that you know the piano because then this should make sense. Imagine if you had to play a combination of white and black keys on the piano in order to play C major. That is, when the music has no accidentals, you would still be playing black keys.
Imagine the only key that used all the white keys was B major. So when the key signature has five sharps, you are playing only white keys.
That is similar to what you are suggesting for transposing instruments. They don't literally have white and black keys, but transposing instruments do have a simplest fingering for one major scale. It makes it much easier to learn and sight read if the simplest fingering also is the key with no accidentals, i.e., C major.
Transposition only becomes tedious when you play with other musicians. Complications arise in ensembles even when no instruments transpose. For instance, the simplest key to play on the guitar is probably E minor, so even just a guitar and piano playing together will be more of a challenge for one or the other musician. Normally one has learned to play in all keys, or at least the most popular, fairly well before doing a lot of serious ensemble work.