They force people to think about what they're doing, talk about any problems they're having (so the group can help), and keep everyone apprised of what else is going on.
It's literally what the 3 questions are for, and it does it admirably. In a previous company, we followed the "Agile" rules for "standups" very strictly, and it worked for us.
And here's why a truly "agile" (not "Agile") version of standups is great: Our company uses it to socialize as well. We get the business part of the "standup" (we don't stand) out of the way and then spend some time socializing for a while.
We were already doing this for a couple years, but now that one of our team is 100% remote from across the country, it's our best chance to socialize with them and keep the team close-knit.
And it's working.