The problem isn't lazy-loading. The problem is webpage authors who don't specify the width and height attributes on <image> tags, which allows the browser to correctly flow them before they load.
Just not until you've scrolled down to their obituary.
Then you read like 2 words of it and the screen jumps as another image trickles in.
This web page is pretty image-heavy though. Lazy loading optimizes for the reader who reads partway through and abandons reading the rest of the page.
Optimises what exactly?
data usage. Generally worth optimising, to be honest (both for the client and the server).