This guy says he is thinking of using Aurelia instead. Aurelia mentions using web components. If I can use web components now the why do I need Aurelia?
Same reason you might use Polymer instead of raw web components: Polymer adds nice polyfills, binders and observers and overall nice helpers to make handling web components much easier than the raw standard.
I tried using straight web components with the polyfills; it gets kinda messy compared to something more polished as Polymer. I assume it's the same deal with Aurelia.