I wouldn't say
everything gets recorded in mono/single track.
I drum kit can sound great done with a true stereo OH pair....piano also works well, but like anything, you have to make it fit within the context of the song.
While dual mono isn’t true stereo, sometimes that's a better way to go so you don't fill out the entire stereo image left to right with true stereo tracks.
Dual mono gives the impression of stereo, but is more controllable AFA where the two tracks sit in the mix.
If you find you are using dual mono tracks and trying to make them sound like true stereo...then you might be better off recording those things with a true stereo mic setup...but your quality of stereo image will depend on the mic placement and of course, the room...and the type of instrument (not all come across well in stereo).
That said, I remember a few years back on another forum...Bruce Swedien was on the forum and talking about how he recorded sessions using many tracks of stereo pairs.
You can read his answer to the first question here to give you an idea of his approach:
http://www.sweetwater.com/feature/swedienvideo/
I've heard it said, "Why does Bruce need ALL those tracks?" Here's why... I guess if there is a common thread in the sound of my work, it would be the fact that I absolutely love the emotional impact of true stereo images in music recording. Because of that, I use an awful lot of tracks. Most of my recording work is done in stereo pairs as a matter of fact. True stereo recording plays a big part in the overall image of my work.
So while most people do a lot of mono tracks...there's nothing that says you can't work with lots of stereo pairs.

The trick to it is that you have to be already mixing in your head AS you set up your stereo pairs.
IOW...you don't necessarily set up all your stereo pairs so that each instrument sits in the center of its stereo image. Instead, you might do a stereo vocal centered...but then you might do a stereo guitar and "pre-pan" it to a specific point in its stereo image...like hard left or 3:00 right...etc.
When you then mix your stereo tracks, most of the "panning" is already working for your...of course, you still have the ability to move things around some if needed using the pan knob.
You would have imagine where exactly you want each element to sit in the mix left to right...and then set up your stereo mics per/elementt to give you that imagined position for each element.