I am a user of both social network apps. Why don't these big companies provide a back-to-top button after scrolling down? Similar to Ebay and Tumblr.
To some extent, they DO have that, though not in exactly that form. In many of those apps (Facebook and Twitter, at least, and Gmail in the desktop), clicking on the main Nav item that best represents that "flow" or "stream" page/experience performs double duty.
In Gmail, your main experience is the Inbox, but there are other filters and boxes you can view, such as the Important filter:
Now, if I click on the Inbox link from here, it will return me to the Inbox:
If, however, I now page through my email in the Inbox to deep in my email list, and THEN click the Inbox item again, it will bring me BACK to the first items of my Inbox list. This actually includes THREE functions, since clicking it while you are already on the first page of results will trigger a reload that will check for new mail.
Similarly, if you are scrolling through your Twitter app on, say, the Moments or Notifications "tab" and you touch the Home tab, it will first take you back to that Home feed, but right where you left off when you were last viewing it:
Touching that Home tab AGAIN, however, will rapidly scroll you up to the very top of your feed and show you the most recent tweets:
Facebook works similarly. While this is not as explicit as a "Back To Top" control, it is becoming fairly standard in apps, and makes a certain amount of sense, especially in environments where different methods of tapping, pressing, or holding can result in different actions.
I personally find it quite intuitive.
Because it violates user's mental model of the behavior of a link.
According to Jacob Nielsen:
Users have developed a strong mental model for link following , which has several elements:
- Clicking a link navigates you to a new place.
- After you click, the old page goes away .
- A new page loads into the window, replacing the old page.
- You first see the top of the new page.
- The Back button returns you to the old page.
Basically, he explains that users expect to go a new page when clicking any link but when the page scrolls up they get confused because their expectation is violated. Also if users try to click the browser's back button again the site doesn't behave as expected. Another confusion.
Users get confused where they are in the site.
From his experiments he explains that most of the users wasted more time than save clicking the browsers back button several times and trying to go to the intended location.
Jacob Nielsen's research makes sense because the majority of Facebook and Instagram users have low computer literacy. Thus, when they click a link that doesn't behave as usual they get confused whey did they go, why the back button didn't work as expected and got them back at the login screen.
For us UX-ers and developers it is hard to imagine that this may confuse someone but this is because we have already build the right mental model for "Back To Top" links. In other words we know what will happen when we click such a link and users with low computer literacy don't. This is because this is something new to them, and they get confused.