How about because Amazon develops some of the most interesting and innovative products out there? AWS, Alexa, Go Store, to name a few?

I've worked on several AWS services, and I'm very proud of being a part of them and of AWS in general. I bet there are very few other places where I would find problems this interesting or of this scale.

If you have some experience, you probably know better than just look for a job at company X - you probably choose specific role in a particular team or product. And Amazon sure does have a lot of great products with very interesting positions.