Why does it have to be water?

Okay, I know...another Mars post.
But, earlier today the news agencies picked up on a story about features seen on Mars that may have been formed by liquid water. The image at right is zoomed in on one of these deposits. The lighter-colored material is being interpreted as possibly the result of flowing water.

Why does water need to be involved at all? In fact, why does liquid need to be involved? Depending on the material that makes up this steep slope, it could simply be a gravity failure of loose, granular material that flowed and created this deposit. Sand dunes do this all the time. What is the gravity like on Mars compared to Earth anyway....how might loose, granular material behave?

My point is that water is not necessarily required to produce this feature.

What's worse is that once the words 'water' and 'Mars' are spoken in the same sentence, reporters and newspapers make giant leaps of inference and start talking about 'life on Mars'.

Granted, I haven't actually read the scientific report that is coming out....my guess is that the news is overstating what the authors may be implying in their work.