Because apparently it is programmed deep, deep into Adobe's DNA that they cannot possibly manage to come up with a straightforward, clean, and logical installation process. It is demonstrably beyond what's possible for Adobe. I say that based on years and years of dealing with their byzantine, buggy, and bloated installers. The Cloud was supposed to magically make things better.
I also now have two versions of After Effects, Audition, Flash, Illustrator, Media Encoder, Muse, and Photoshop residing on my computer.
Why?
Well, because the Creative Cloud installer didn't really "update" the current software...it just installed new versions next to the old ones.
Why?
Beats the hell out of me. But I'm pretty sure if I expend my time to contact Adobe's support folks I will be told to go through some process of manually removing each copy of the old software. They won't know why the "upgrade" process worked this way, and they won't care. They'll just cheerfully advise me to waste my time cleaning up Adobe's mess. Again.
Looking forward to the day I no longer need to use Adobe products.
Are you listening, Apple?