Why do web sites check for mobile devices but not for desktop?

Question

With the spread of mobile devices, web sites have been checking whether the device is a mobile device and offering to display the mobile version of the site for years now.

Recently, a friend of mine sent a link to m.gag which I opened on my desktop. I was amazed that the site opened in the mobile version and would not even suggest using the desktop version (9gag). I looked further into it and this seems to be also a pattern with news paper sites, e.g. https:-//mobile.nytimes.com/ vs. https:-//www.nytimes.com/, (two Austrian news papers: https:-//mobil.derstandard.at/ vs. https:-//derstandard.at/ and https:-//m.kurier.at/ vs. https:-//kurier.at/)

Now to my main question: why is there this asymmetry of suggesting to display the mobile site or redirecting to it directly but not doing the same for mobile-to-desktop transitions?

(Sorry, since I'm new to this site I can't post more than two links in one post)

EDIT: This question does not ask whether two distinct sites for mobile and desktop are good or bad, and does not ask if there are advantages to having a distinct mobile site but my question comes down to:

Is there a reason why sites offer to display the mobile version when browsing the desktop version but do not offer to display the desktop version when surfing the mobile version?

Answer 1

The reason for the asymmetry is almost certainly because a link to the "main" site is much more likely to be viewed on a mobile than a link to the mobile site would be viewed on a desktop.

Assuming an established site has taken the decision to create a "mobile" version (as opposed to making a fully-reactive site), then www.example.com is going to be "out there" (on other sites; in search engines) much more than mobile.example.com. Therefore, it seems more sensible for the main site to do an Are you on a mobile? check and redirect to the mobile site than it would to make the mobile site check to see if it's being accessed from a full-size device and re-direct back to the main site.

(And a very good reason for not doing both tests is that sod's law says you'd end up being bounced back and forth from one site to the other :-))

Answer 2

Some of this is old practice from when mobile was a minority and developers weren't sure how to handle it. Some of this is because the site can't handle mobile in an adaptive/responsive way to adjust to smaller screen sizes. It can be a lot of work converting an older site to the new methods, techniques and technologies so it can be far easier to just redirect to an entirely different mobile version.

But that's the problem. You have two different sites to maintain, essentially, and, eventually, most of these sites redesign and adapt to screen size and functionality rather than mobile versus desktop.

There is a blur between the two and it's often difficult to detect the difference between the two and it shouldn't be done in many cases.

Answer 3

It is because, mobile ad revenue is growing, and desktop ad revenue is not growing. Because "mobile" it is growing, it means it is easier (cheaper) to capture a mobile user rather than a desktop user. Finally, the monetary reward of a mobile user is x times larger than desktop user. This creates a lot of incentive to capture mobile users and almost no incentive to capture desktop users. (if you have one extra dollar to spend, today it is better to invest it in capturing a mobile user no matter what.)