>I'm never going to sit down and review the cards

Well, don't sit down then. Standing up flip through the cards you filled during the day and toss them into garbage, unless one is really important. You're strictly better off than writing down nothing at all during the day, which is the default state for most people.

Later in the day when I pull them out, many do get trashed. Lots of Todo items never make it to my digital Todo list because my brain processed them mostly in the background during the day. I find the physical nature of the cards means I can't avoid that processing step. The times I revert back to digital first, my notes end up everywhere (I input them in the fastest way, rather than finding the right place) and immediately begin rotting because now I have remember and force myself to condense and organize rather than it occurring naturally.

For me, it's a bit more adhoc than the suggested above. Recent uses: jotting down measurements of some furniture; writing for somebody the name of a book I was recommending them; shopping and todo lists; doodles and sketches. notes tend to be odd phrases from conversations. The reviewing is minimal -- under 10% of what I write needs preserving, the cards mostly get a quick glance and then go straight into the recycling.

I use the same index cards when I'm writing something, for paragraphs or ideas which I can visually arrange on a table.

I've been doing this in some form for a couple of years, but just as a low-key background thing. For me it's just the minimal viable equipment for being able to write things.

I could use my phone for almost all of this, but index cards are a lower risk of distraction.