Because they will be able to put ads in front of your face all the time.

And that means that first, they'll make it do enough desirable things that you will accept ads.

And those will make you want it.

That's not a very convincing argument and doesn't answer the question at all. I already can't think of a reason I'd buy one, and telling me it'll be full of spam isn't helping.

I'm also a little disappointed they've raised so much money if their long term goal is just spamming people in "augmented reality".