Space

Also, probably nobody capable of traveling the stars wants to settle a planet. Once you figure out how to make huge spaceships (which you’ll need to travel interstellar space) you’ve essentially learned how to make cities in space.

I don't think it is a valid point. Yeah, if we can build a ship that take us to Alpha Centauri it would lool like a small city, but that does not mean that it can last forever and the traveller would never need to settle on a planet. And looking what the humans did in the past, it seems logic that while a part would want to continue to explore, another part would want to settle on a planet.

Our solar system would support a lot of people if we just used the resources available for space habitats, and by “lot” I mean in the quadrillions. And it turns out that all you need to support that population is a star to provide energy, and some planets to source materials from.

So with that in mind, why bother finding another habitable planet?

Because it is habitable and can be used as a transit point, advanced outpost, refuelling base or any other use you can do of an habitable planet where to do things you have not to fight even with the environment (tourism for example).