I think this totally depends on the site in question. Seriously researching something is hell on mobile browsers. As is doing productive stuff. Who wants to work on a tiny screen and no keyboard? On the desktop you can open dozens or hundreds of tabs on a single topic. Therefore I'm not surprised to see that on my site (technical articles) I can see the number of requests from mobile devices is just 17%.

Windows is 52%, Linux (without Android) is 18%, Macintosh is 13%, Android 11%, iOS 6%, Chrome OS 0.5%, others <0.5%. (Android and iOS may include tablets, but the overall traffic from tablets is just a few percent.) (Note that I've excluded crawlers and unknown user agents (bots and crawlers) from these results.)

FWIW, some bots lie about what they are, which typically inflates the Windows results. I have another source of data, I can see what types of devices saw my site in Google results, and it's 69% desktops, 30% mobile, 1% tablets. (I can also see how many clicked, and it's similar numbers.)