It might be because we keep discovering more exoplanets. So far we have confirmed 5830 of them ( https://exoplanetarchive.ipac.caltech.edu/ ).

Why is discovering another headline-worthy then?

For many reasons. 1 - it might be very unique itself 2 - it might be very close to us 3 - it might be orbiting a very interesting star, a star type we didn't expect to have that planet type or so many planets, or so close, or so far, etc 4 - the more exoplanets we discover the more we learn how star systems come to be. the more we know how rare ours is, how it might have formed, etc. It helps us answer age old questions.

"In the habitable zone".

I believe we have some of those, too, but very few. Another one is still a bit of a big deal.