I have iCloud photos and optimize turned on, and still have 94 gb of photos on Mac, why is that?

The "Optimize" feature is fully automatic. As long as you have plenty of free storage, Photos will not needlessly optimize the library, so you do not have to download your photos when you want to work with them. Only if free storage is needed, Photos will optimize more photos to free storage.

Even fully optimized, your photos will need some local storage on your Mac for the optimized versions. Expect to need at least ten percent of the size of the library in iCloud to be used on the Mac.

You can force Photos to optimize the library fully at once by deleting the local copy of the library and creating a new , empty library and syncing this with iCloud. Your library will be fully optimized, right from the start, but your projects cannot be restored from iCloud. If you have to save projects, keep a copy of your library on anexternal volume. See: How to force Photos for Mac to Optimise the Storage Immediately