Why do most websites favor "one page" over "multiple page" loading formats?

[G]

I dont know if theres an actual term for this, but what I mean is instead of using multiple pages to show a large amount of content, many website use one giant page that expands.

For an example, look at twitter. If you want to view the old posts someone made, all you can do is scroll down and let the page load. The page will start off small, but eventually get huge if you go far enough.

Another example is youtube. Go to someones youtube channel and click on their video page. It will show about 30 videos, and then you have to click "load more" to view the rest. The old page loadout was similar to a google search, there would be separate pages that were numbered [ex page 1, 2, 3 ,4...] in chronological order.

The last example, the one that I hate the most, is yahoo mail. As far as I know, there is no option to use a page system. To go through your mail, you have to scroll down, and it will load more email. This is extremely annoying because most peoples email inboxes are huge and viewing it all on one page, as well as being forced to scroll starting from the top is a huge waste of time. They used to use a page system but they recently changed to the the one page format.

Im wondering why a lot of website use this format now as I find it to be an obvious downgrade if yuo want to view things in a categorical way.

[Sadsongs]

Actual size of markup and text content is usually quite small compared with all other file (eg images, CSS, Javascript includes). Additionally, many pages with behaviour like you describe aren't actually loading all content at once - they use jQuery to get the "revealed" content on demand.

Yahoo are just crap coders.

[Calvin]

Because it's perceived that users (especially those with tablets) would rather scroll through page(s) than click to move to the next static page.

It's something of a 180 from early web design days when 'scrolling is bad' was the consensus design view. The fact that online access speeds are 10 times what they were a few years ago helps in that regard. New techniques, more RAM and new browser display engines also make it possible to have "endless" scrolling that is really just a form of a "windowed view" where what is displayed is held in memory.

Fault the programmer if you have to 'start from the top' when moving forward/back on a site.There are straightforward ways of remembering where users are when they click away and come back to an 'endless scroll' page.