The main benefits of lazy loading break down into two areas…
Speed Up Your Page Load Times
The main benefit is a significant upgrade to your site’s initial load time. If you use lots of images in your posts, they’re going to add a bunch of size to your page. There’s really no point to loading them before it’s possible for visitors to see them.
So, better to load the page immediately and then fill in the web contents as they’re needed. You can’t even be sure readers will scroll the whole way down, which makes loading them entirely unnecessary.
That leads us to next point…
Save your Users’ Bandwidth
Not everyone is using unlimited bandwidth. For people who are limited by say, 3G mobile plans (or just horrible Internet providers), you can do them a favor by lazy loading your web contents. They’ll only have to use data for web contents they’re actually seeing.
They may never know, but it’s a nice thing to do, especially on your mobile site.