CTRL scroll zoom on Mavericks gone
Solution 1:
Press ⌘ command+⌥ option+F5, then select Enable zoom scroll gestures.
Solution 2:
OS X thinks that the mouse you are using doesn't have a scroll wheel.
Solution 3:
I'm here years later after returning to my MacBook Air and finding this zoom feature missing. Type in "zoom" in System Preferences search and picked the "zoom to enlarge screen" option from the list and it took me right there!
Solution 4:
I've just spent several hours on chat and phone to Apple support about this issue on a brand new iMac, with a clean Mavericks installation and a three year old Mac Mini with an upgraded Mavericks installation.
The common thread between the two machines (neither of which show this missing option) is that they both have, or used to have, the Microsoft Intellitype/Intellipoint drivers.
My iMac is having issues forgetting about these drivers on boot/wake from sleep/when the moon is half-full, and it seems like maybe they've interfered with the way Mavericks determined the scroll ability of the mouse.
I started setting up the iMac with an Apple wireless magic mouse, but reverting to that doesn't make the option appear in Accessibility either.
Apple are escalating this to an engineering team: if I get any answers, I'll post back.