There are three main reasons:
- User experience
Mobile is the fastest growing market segment for web traffic. Radio NZ has 40% of its traffic from non-desktop browsers.
Desktop is 60%, Mobile at 28% and Tablet at 11.8%.
In the case of devices used over a mobile network, the connection speed is going to be a lot slower than broadband. We also still have people on dial-up, and slow broadband (1-2 Mb/s or less).
These are what I call 'The Slow Networks'. I suspect that up 35-40% of visitors could be using a slow network. That is 40% of visitors who could have a bad experience if no thought was put into their experience of the site.
So, we optimise for page size, deliver speed and rendering time, and this underlies all my technical decision-making. (Edit: You'll probably find Radio NZ is one of the fastest news sites on mobile, and URLs all work between mobile and desktop for ease of sharing.)
The psychology of website speed has been long understood. And lately, here, and here. Fast sites are perceived as more credible.
They are also easier to use - visitors can quickly see the page and decide what to do. Now obviously other factors come into play here. Every page needs to treated as page one in a journey - once the visitor has finished with the current page, what can/do they do next? That is a tough question for which there is not a single answer.
One factor in Search Engine Optimisation (SEO) is page load time. The faster your site is the more pages an indexing bot can crawl in a set time period. Google consider page load time so important they include them in Analytics, and it is believed this is used in calculating your page rank.
We actually use other methods to tell Google what the latest content is, so they can index that first, but this does not remove the need to optimise all pages.
Every few months, to keep on top of performance, I compare the performance of www.radionz.co.nz with other NZ media websites. I also benchmark the site against past performance, and follow a number of thought leaders in the performance area to keep up with the latest thinking and techniques.
This is no longer bleeding edge stuff for nerds to talk about over beer. It is mainstream and every site can benefit from improving page speed.
For some it is as simple as restructuring the order of elements in the head of a HTML page. For others, a few web server configuration options could help. Yet others may be almost beyond help with 10 megabyte pages, duplicate JS library code, unoptimised images, and bloated CSS.
And then there will be those that will not care. All the studies say you are leaving money on the table, but in the end that is your choice.
There are plenty of resources available for free. Just start with a Google search, and good luck!