Images are inevitable if you want to retain your readers interest. Images convey the idea in just one glance. But search bots can't see images. From my experience I can say...bots are incredibly stupid. They just don't use their brain. And how can they? They don't have any!
So if you image is about your cat, bots won't understand that. We need to tell them that this image is of my cat. Weird right? so this makes it important to use alt attributs with image tag.
I am a great fan of Matt Cutts. But here I would wish to clarify the small mistake he has made here. Alt is not the tag. It is the attribute for the image tag. If you know HTML you will understand what I mean. Else just leave it..even if you don't know HTML you can learn how to add alt attribute to blogger blog images?
Video: Importance of alt attributes.
