True. However, that has nothing to do with the OP's question. I am not familiar enough with the history of the clarinet to answer with any kind of authority about my secondary instrument, but I certainly can about my primary one.
When the inventor of the saxophone--Adolphe Sax--created the saxophones, he created 2 different lines: one for the military, and one for symphonic use. The military horns were pitched in the traditional concert pitches of C & F, while the military ones were in the transposing keys of Bb and Eb.
Eb/F saxes Sax built or conceptualized included: Sopranino, Alto, Baritone, Contrabass
Bb/C saxes Sax built or conceptualized included: **, Soprano, Tenor, Bass
** I have not seen it noted myself, but some historians have stated that Adolphe Sax did indeed conceptualize a sax that was an octave higher than a soprano: A saxophone that Benedikt Eppelsheim from Germany now has perfected called a Soprillo.
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Let me speculate wildly for a minute about Aulos303's original question about why people tend to start on Bb clarinets rather than on C or Eb ones. Simply put: because there is very little music for clarinets other than those pitched in Bb.
When you learn to play an instrument, you are obviously wanting to play with others. Bb clarinets are the most commonly used in most styles of music. Period. Full stop. Yes, I work with clarinet players who have multiple-pitched instruments, but those are pro players.
Since I don't play in symphonic settings, I can't comment on when they might be used there. But in pit orchestra work, sometimes a Reed Book player might be called to play part of a song on his/her C or Eb clarinet, and then switch back to their Bb one.
Going back to the saxophone example, when people start out, no one would be advised to start on soprano sax, since there are no parts for it normal band music. Even adults are steered away from the instrument, and advised to learn it only after they have mastered the embouchure control and fingerings on an alto or tenor.
Hopefully this clears this matter up a bit.