why backlog refinement is an activity in scrum and not an event?

Hi Folks,

I am just wondering, why backlog refinement is an activity in scrum and not a event? 

My logic is, the focus of a sprint is the sprint goal. In backlog refinement you talk about future state which can change. More-over

it's not a time-boxed activity. We generally say to have 10% capacity allocated. That's my reasoning. Happy to have your views on same.

Thanks,

Beenish