What is the purpose of the file manager?

I know this sounds stupid but I honestly can’t seem to understand what the file manager in EE is useful for a website.

Uploading images trough EE is way more pain than doing it with your regular FTP/SFTP client which can make multiple uploads.

But somehow I figured out that it could be useful to process images automatically. So I did some tests. First EE only recognizes files in the uploaded directory when you manually click the sync button. I would prefer it to be done automatically but it seems that is not the case and you need to manually hit the sync button. Ok, fine, it can then process all images and for example watermark them if you created a watermark rule.

That is the first bug I found. Even if I don’t select the watermark option in the sync, it still process all images and applies the watermarking. Now EE creates 2 additional folders called _thumbs and _watermark

Not sure why it creates thumbs (maybe a default setting) since all I did was to create the watermark option and no tumb option. Now, my question is this.

How is this exactly useful?

In the docs it says:

A watermark is a unique text string or graphic that is automatically added to your images to mark them as “yours” and to hamper other people from being able to “steal” your images

https://docs.expressionengine.com/latest/cp/files/watermarks/index.html

Wait a minute. The watermarks are not created on the original images but in the _watermark folders as copy so how exactly will this protect your images? I assume you have to delete the originals manually otherwise anyone can still link to the direct images…then EE complains the image is gone from the database.

Maybe I’m confused but how exactly is this feature used on live production sites or for what purposes and why I should I prefer to have the images to be managed from the EE file manager?