1) it's great for refocusing everyone on monday first thing after a long weekend of hopefully for getting about work
2) it's much easier to follow up with people as a ritual rather than a 1 on 1 interjection, it depersonalizes info gathering that'd be hard for a manager to acquire any other way. Vocal tonality says a lot sometimes.
3) it's a great way to give casual encouragement and recognition occasionally
That said, I only think standups are needed maybe 3 days a week and 10 minutes max usually.