Ask HN: Why HN doesn't allow collapsing comment sections?

Why HN doesn't allow collapsing comment sections?

Right now, HN displays all comments in an indented tree structure so the reader can follow a discussion chain. But sometimes I want to checkout an alternative original topic regarding the link. I would go and look for the second highest ranked top(root) comment. But not being able to collapse comment sections make this really difficult. Why don't we do it like Reddit does?