It isn’t just to limit page size, it also works as a damper on heated discussions, as most people won’t read more than the first page, but comparatively few people stop reading in the middle of a page, regardless of length.
I figured that, but I didn't want to make such an embarrassing assumption about what purports to be a reliable tech discussion site. Especially when I noticed new comments automatically went to page >1. Sad, but hey, it's HN's property.
