Because Spanish doesn’t have that sound. The words where French, Portuguese and Catalan have a ç sound, Spanish has a z sound.
A much more pertinent question would be why does spanish have “ñ” and the others don’t. And the answer is convention. Portuguese and Catalan have “nh” instead, French has “gn”.
The cedilla originated in Spain, in fact its name means “little Z” in Old Spanish because it was a tiny Z you wrote under the C. Words that would have been spelled with Ç are usually just spelled with a Z in modern Spanish though. When and why it fell out of favour there but not in the other languages I don’t know the exact circumstances of.
Edit: What I can add however is that in modern Spanish the sounds for Z and the soft C are the same in the standard language and most dialects. That means there would be no distinction between the syllables za and ça for example, leaving the Ç unnecessary since you can just use Z instead. In some of the other languages you mention there may still be, or was when their spelling got standardised, a difference between C and Z which would leave the Ç useful.
In every language people use letters to represent sounds, so, when you have two sounds and they converge in one, it’s possible one of those letters is also lost.
In the 14th century, in Spain, there were 6 sibilant (“s”-like) sounds, but they changed until the 3 of today (one s, one sound like “th” and one which is a hard “h”, used for “jamón” for example). The ç was used until around 16th century, but, when those 6 sounds converged into 3, it was not needed anymore, since the “s” sound is represented with “s”, the “th” with z or c (depends on context) and the “hard h” is usually j or g. So, there is no need for the ç anymore.
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