* Scouting possible destinations or routes for the rover.

* Imaging areas from above with higher fidelity than possible from orbit, and from angles not possible from a rover.

* Retrieving samples from areas inaccessible for a rover.

I find it hard to believe you genuinely asked yourself this question and came up empty before posting this vacuous comment.

Because exploring is our nature. And because it will be the first test or flying something in an alien atmosphere. Tons of data alone from the first 5 seconds is very interesting. It's the first step to commercial airliners on Mars :)

It's just a demonstrator but can travel 100m in each 90 second flight.

For comparison, the Curiosity rover has travelled 23 km over 8 years.

Well, you may be able to get places a rover can't. But as they say in the article, this is just a demonstrator to show if they can fly on Mars at all.

To test the technology for next missions. This is just a proof of concept.

The article covers this.

In the future maybe they can fly with LiDAR to get more accurate surface details for the rovers to navigate with, and finding interesting features

Perhaps we could eventually get things like a video of a drone flying over the 4km high cliffs of Echus Chasma:

https://apod.nasa.gov/apod/ap080723.html

There is a whole new world out there!

main thing I've seen on mark rober's youtube is that it allows you to really scout out locations with a speed unheard of for rovers.

Also, you can't really(easily) get a helicoper stuck on rocks :)

I would have thought atmospheric data that you can't get elsewhere - you'd be able to learn things about pressure and wind at altitudes that rovers can't get to.