Can anyone tell me why I would use Lightroom CC over Apple Photos?

The sensai searching, presence of the camera raw editing engine (a LOT better than Apple's) and integration with Lightroom Classic. Lightroom Classic is still best of class in raw editing.

Well the machine learning aspect is also pretty good with Apple, and you can count on them perfecting it over the next few years.

Regarding LR:classic, I am not sure how my workflow would look like when using CC and classic in parallel...

Haven’t upgraded to High Sierra yet but after creating an Album in Apple Photos I didnt find it easy to just share a link to that Album.

Also, the iOS photos App is a mess to me. It offers and shows me things I don’t want to see..... loads of random albums, moments, memories, collections... messy.

And I’ve used Apple for nearly 25 years and iPhone since 3GS so like their products!

I have high sierra and the photos app is unchanged. With that said, my android phone and photo editing is much better then this new Lightroom mobile and my Amazon prime gives me free unlimited storage of my photos...and syncs! So in answer to your question. The only thing I find useful here is being able to right click on a photo and select edit in photoshop. And having the edited file added back to my catalog. Also, notably, I can share my photos from my phones native gallery much more efficiently and with more apps, then the new Lightroom. The biggest issues I see here is that I cannot share to Adobe Stock, and I cannot maintain multiple catalogs. In lightrooom classic I have more then one catalog and can easily switch between them.

I somewhat agree. I think Lightroom CC is meant for people like me who were starting to look at Apple Photos as a replacement to Lightroom Classic.

I am not a Pro, but I shoot Raw and take photo editing and management seriously. I was starting to question paying Adobe so much and also having to pay a cloud service for storage. Somehow Adobe read my mind.

I trust Adobe more when it comes to raw photo edits. And I think it does not lock you in to Apple OS. So if I ever switch to Android, I can keep having access to my photos without having to migrate to a non-Apple manager. The same can be said for Google Photos.

Lightroom CC offers better editing capability over Apple Photos - especially the linear gradient/ radial gradient and the brush tool are effectively used and appreciated by photography community. Presets and profiles offered by Lightroom CC adds another advantage to Lightroom CC.
Basically, Lightroom CC does all that is offered by Apple Photos and some more...

I was an avid Photos user for years, but there are two things that makes LR better for me:

• RAW engine is the primary reason, as it's miles ahead of Apple's. I've tested with hundreds of photos and in approximately 95% LR wins hands down. Other 5% they are the same. It come down to better noise reduction and local edits.
• Currently there is no way of making presets in Photos. And you cant Copy your edits from one photo to a set of photos, you have to go through one at a time.

You can have better noise reduction with DXO plugin, you can remove objects better with Pixelmator plugin, but the dealbreaker is as soon as you come back from one of the extentions you are stuck with a JPG. 

That is why I chose to stick with LR after much consideration, even if it costs more, have the worst integration into iOS, have the most limited import/export options, has bad management (no smart albums for example), has a very bad Apple TV app..

Hope that helped, as I was in the same situation as you.

*EDIT:
Sorry, forgot to mention, I've instaled the beta of next macOS just to see what are the improvements in Photos App. There are none (that make a difference).

Love drag and drop  rather not live without it Often need to send a photo through email easy easy in Photos and in the new Cloud version of LR it's a nightmare to send a photo  recipient has to sign in to open???!! crazy! Really dislike LR hate the new dark gray background in the Cloud version . Also hate the way Apple doesnt give a choice to NOT SYNC with all devices . Dont want my camera images synched to my phone! GIve us an option without closing us out of the cloud if we choose that!but still be able to save to the cloud!! Apple needs to fix that! DRagging a photo out and dropping it into an email is seamless and wonderful . Lightroom is too complicated to use . Dont like it all.. Apple needs to upgrade and tweak their Photos They abandoned photographers That stinks!