People generally don't spend time roaming around within the OS, or standing on desktop screen. I sometimes goes many days before I even lay eyes on my wallpaper. 90% of the time I open my laptop, browser is already open and I get to work.
Widgets are and always were a gimmick. User behavior won't change without a strong need. I don't think anybody need any widget. Nobody will miss them if they are gone.
Not necessarily. I've got a sidebar taking up otherwise unused space on this way-too-wide screen that shows memory usage, CPU usage, network traffic, top processes, hardware temps, and a pile of other useful stuff. It's incredibly useful to be able to glance over and see what's going on under the hood if something appears slow, or hung, or other odd things are happening.