Exactly this. To give you a datapoint from our properties: Our web site attracts 90% of the users, but only 60% of the actual traffic. In all metrics like retention, frequency and time on site, mobile leads by factors of 2-5.
Part of that is definitely self-selection, but as some people already said, other notable effects are push notifications, mindshare, loss aversion (you're on somebody's device already, so they can just as well use it) and partly better performance.
So much about the users, but Monetization is much better as well, mostly due to mobile ad-IDs, which especially on iOS lets you extract double the revenue per user due to targeting. Ad blockers are harder to bypass.
In the end, a mobile app will get you anywhere between 2-10x the revenue per user you attracted to your property, so that's why Reddit is pushing so hard.
To stay in Reddit's lingo though:
`LPT: https://old.reddit.com`