. . .BTW, when you assign a photo to a folder in Photos, it just makes an alias, not a duplicate. Still stupid.
A matter of personal preference. I like having one place I can go and see all my photos, no matter what album I put them in. The alias thing also allows you to put photos in multiple albums, which can be handy; say if you have an album for your children and another for vacations. You don't have to chose which album is the best.
I admit it adds a bit of uncertanty when sorting photos into albums, since there is no clear indication whether a photos has already been added to that album, but it's a trade off for other uncertanties; like having to search thorugh multiple albums looking for a photo with multiple possible locations.
For myself, I periodically go thorugh the last couple months of photos and add them to my albums. If I accidently make a duplicate in an album, it become obvious quickly when viewing that album and is easily corrected. And since it doesn't actually make duplicates, it is not like I'm wasting storage space.
This isn't me trying to tell you, or others, how I think things should work. Just pointing out that any approach to filing your photos has advantages and disadvantages. Photos has one approach, other apps have different ones.
Of course a full featured powerhouse of a photos app would let you do thing 'your way' no matter what that is. The downside of those apps is they have a steap learning curve. You spend the first several days learning how to beat those apps into submission.
So, usually, it's easier to find an app that either 'moslty' fits how you want to work, or learn how to use the app you have on hand. Because my photo collection isn't huge or complicated and I value the convinience, I chose to conform to Photos. I'm reasonably happy with the results.