Personally I look at it like this. While I'm not physically 'stealing' their product, I am still profiting by not paying X amount for its use.
As an example, imagine if you are planning on purchasing a copy of Photoshop at $1000 but before you leave to go to the store you do a quick search on your favorite torrent site. Sure enough it's there and you download it, saving yourself $1000 while still benefiting from the use of the software and using the $1000 on something else.
So while software piracy might not harm the developer directly, it greatly benefits the person who downloads the software.
As an example, imagine if you are planning on purchasing a copy of Photoshop at $1000 but before you leave to go to the store you do a quick search on your favorite torrent site. Sure enough it's there and you download it, saving yourself $1000 while still benefiting from the use of the software and using the $1000 on something else.
So while software piracy might not harm the developer directly, it greatly benefits the person who downloads the software.