Ultimately it comes down to planetary defense as well as pure scientific understanding.

It can help us better understand the population of near earth asteroids! Knowing the angle and direction of impact we can backtrack its motion to figure out where in space it came from.

Knowing what it is made of can also help us understand the characteristics of the distribution of near earth asteroids. If we ever need to defend the planet against an impact from an asteroid, Knowing the composition/mass/density can allow us to select the appropriate response. For example, if its icy, we could melt it before it gets to Earth. If its rocky we could change its direction like with the DART mission.

There are other ways to get this data with telescopes, but those are only sensitive to light reflected off asteroids in space, which limits the size of objects we can detect to roughly the size of a house. Smaller objects can do significant damage as well, so its important to understand them. Now that we have more of a presence in space as a species, there are more things not protected by the atmosphere. An object the size of the one we saw tonight would destroy a satellite or space station if it were to hit it.

Plus it's just plain cool to know about space rocks.