The UA web site, while reasonably good in terms of functionality, does not appear to have been designed with efficiency in mind. I have a fat internet pipe, and a reasonably beefy desktop, but that doesn't seem to be enough to get snappy responses, ever, from UA's site. For example, initial loading times are often in the 20-30 second range, which, from a user experience perspective, is unacceptable. There are various tools that developers use to understand responsivity in web pages, and putting UA's through those tools shows red across the board, suggesting it hasn't been an issue of concern.