2. I think you're pretty off base. The gains for running are just as correlated to your training, and (IMO, obviously, it's unquantifiable) a 10% speed improvement feels exactly as good as a 10% weight increase.
(For reference, I've been a medium good runner and lifter: at my various peaks I've run consistent sub-18 5ks and squatted 5x315lbs)
One of the reasons why weight lifting makes the process more obvious is that lifting is inherently a high intensity workout.
This is absolutely untrue, and purely personal anecdotes. Otherwise agree with your first two paragraphs.
I did make very very quick gains by "just lifting" and so felt very differently about it. These gains were both in strength and body composition, and within only a few months I found that I could impress people. Not at all like running: it's years and I still can't run an 8-minute mile.
I've lifted and run at various times in my life, and I found running a lot more rewarding, especially with all of the bad advice out there that surrounds lifting.
After the past 5 years of mostly running (with some time away at times due to injuries), I went from a 12 minute mile to a sub-7 minute mile in 3 years (with 1 year not doing much in the way of exercise). Consistency with the frequency of exercise matters a lot.
A 5 minute difference. Which is amazing. But only to other runners.
Going from a 50kg (110lbs) squat to a 130kg squat (286lbs) in 3 years is almost trivially doable (I've once gone from 50kg to 100kg in 3 months) and is impressive to everyone.
As much as we'd like our motivations to be pure, we really really really like impressing our friends.
It's very easy to measure progress when you're lifting. You're putting more on, the numbers are going up. Lifting more weight leads to being able to lift more weight. The path from "lift less" to "lift more" is obvious, easy to measure, and feels a bit like building an MMORPG character.
For running the gains are a lot slower and less correlated to your training. Running 2 minutes faster today than three months ago also doesn't feel as significant as squatting 50kg more than three months ago does.