Have you perhaps previously used Picasa on Windows? Photos is very different. It is a photo manager, not a file manager.
Photos focuses on the attributes of photos and the relations between your photos. It keeps track of the various versions of the same photos, the adjustments you applied, and you can organize the the photos by photo specific criteria using smart albums. You could search for all photos taken of a specific person taken with a specific camera using a flash. Or search for the content of the photos - all photos showing a bear or bear, a sunset, or a birthday cake. You do not have to tag the photos with keywords - Photos is scanning the photos and trying to recognize the content.
At the heart of Photos the lossless workflow. Photos never, ever will modify the photo you import. It will be preserved and you can revert to the original photo. When you edit a photo, Photos will create a Preview to be used in other apps from the Media Browser, but the final, edited photo may not exist, until you export it. If you want a copy, you export a version in the size and quality you need. As you add further edits, Photos will always start from the original to give you the best quality. You can revert individual adjustment and keep others. I find this very convenient, but if you want a file manager and not a photo manager, use the Finder and folders instead of Photos.
Photos in Photos are not just files, they are represented in a distributed way: the original image file, and many linked database entries, plus auxiliary files, thumbnails, faces, etc. And if you are using iCloud Photo Library, a part of this will not even be on your Mac. So there are no finished image files of your photos to access through the Finder. Other apps can use the Media browser or their own Photo Browser to access the Photos Library.