* Pulling out your phone/phablet/tablet & navigating to your note-taking app takes too long. (Heaven forbid you want to try this with a laptop, if you happen to want to tote one of those around all the time.) * Once you clear that hurdle, then you've got to type something you'll be able to make heads or tails of. * Or you can talk at your phone and take a voice note. This assumes that the environment is both quiet enough for it to work well and appropriate enough for you to be dictating without annoying a bunch of people. The fact that you're likely to look like a crazy person talking to yourself (or worse, your phone with nobody on the other end) doesn't help either. * Pen & Paper is quick, but easily lost as you said. You can take a picture of it, but context needs extracted somehow then. * Now you've got to organize it all. Or you can just toss them into some sort of bin (digital or otherwise) and tell yourself you'll do it later. As if!
If you front-load the organizing effort then it's too time consuming and cumbersome to do /really quickly/, so you don't bother taking enough notes.
And not nearly enough people come back to their things later to organize, so you end up with an explosion of a million unorganized scraps (digital or paper).
What I'd love is an app that I could slam all kinds of things into quickly (like Keep) and that could weave through my life and try to stitch the scraps together, using things like my location, calendar, text extraction/transcription (from pictures/recordings) to build context and try to organize the scraps. If I happened to have the time to take the effort, make it easy to organize the thing I just added into the right place.
Preferably one that could learn from the prior organization, so that as I put more into it it gets better and sorting things out correctly. If I'm taking notes or pictures or recording things during (or very close to) a time I've got blocked out for a meeting, then start associating those things together.
...and a pony. I want a pony!