Why is there so much excitement over helium having been discovered on an exoplanet? Isn't it oxygen that we should be looking for, since this is what is needed for life? What do we need helium for?
You are right that helium around a gas giant is no kind of surprise, and oxygen on an Earthlike planet would be spectacularly more important. However, the excitement is simply that if you can detect one element, it means you might be able to detect another. It just gives you more ways to learn about the planet, and offers promise for more new ways to learn. One might find analogy with the first detection of exoplanets, which were "hot Jupiters." No one was surprised stars can have planets, and no one thinks hot Jupiters are conducive to life, but if you can discover one kind of planet, it bodes well for the later discovery of others. Anything we can learn about composition is an important step in the right direction.