Well, labs cannot be popular since I've pretty much never met met anyone who even knew that Labs existed in Gmail. It's kind of like saying "Creating labels" with Microsoft word is not popular so we're going to retire it. And by the way within weeks someone released a Chrome Apps to allow Gesture in Gmail. The only issue is that you have to allwo it to access all your data for it to work. Security issue: yes?
But per your definition of popular, Google could retire Google Plus.
Gesture and Touch is not popular? I'd argue that touch is what has changed the phone and PC business in the past few years. Simple UX improvement which the iPhone nailed made it a success... even thought these technologies existed in the past.
And guest what is the hot tech video trending this month, another touch interface: http://youtu.be/_d6KuiuteIA
But I'd also argue that not all features need to be useful to everyone. if they are a huge time saver for a few that good enough. "conversation" was not very popular for many people at first. I've know lots of people asking how they could disable it. Right or wrong... Google stood by it... but also finally acknowledged that perhaps they should offer to disable it. Same with preview pane which they 'borrowed' from Outlook.
Shortcuts in Gmail are nto quite good enough because you can't disable the ones you don't need and they are not using a CMD or CTRL key to prevent mishaps.
I'll stand by it: Gmail Gestures were awesome. Browsing my Gmail inbox is now dull and sluggish.