Bitcoin has the following attributes:

Scarcity

Provable authenticity

Provable ownership

Fast transferability

Leaving aside whether these attributes are worth the actual costs to create, it is clear that such a thing has utility as a way to transfer value. Suppose I have $1,000 and I want my friend in India to have it instead of me. I can announce to the world, "My friend in India now owns $1,000 more and I own $1,000 less." One can imagine a world where that declaration would be all that is necessary. Ricky Gervais imagined such a world in The Invention of Lying.

Of course, we don't live in such a world. In our world, I must transfer a token of ownership of the $1,000 from myself to my friend. The token is a technology, a way of representing ownership of the money. What attributes must such a token have? (See above.) Bitcoin is such a token. It is not a scam. But whether it's the best solution to the problem it solves is a wholly other matter.