Intros and outros had a distinct advantage in the television age, but their benefits are not as clear in the context of modern video and audio content consumption.
I do see one point specifically for outros and specifically for YouTube. It gives you enough time to click pause before automatically jumping to the next video on the playlist. But that's more due to YouTube's stupid behavior than an actual advantage.
SponsorBlock is a browser addon with a crowd-sourced database of skippable Youtube video segments (sponsorship, intro/outro, "like and subscribe", etc.), and the ability to auto-skip them.
if you pay attention you will notice virtually every video with and outro does at least one of these things.
Longer watch time is better for the algorithm. It's also beneficial from a branding point of view. Like it or not, branding is good for YouTubers to stand out.
All that said, some blessed soul invented sponsor block and it saves time and sanity.