The science answer would be there’s probably not that many suitable planets. And probabilities of ships not making it means sending additional ships is a good idea.
Hard disagree on that answer. We have found thousands of possible planet candidates already and we aren’t looking that hard, relatively. The second we have the technical capability to actually get to any other solar system there will be a new instrument in space with the explicit purpose of finding planets we want to travel to
Edit. This new instrument will not magically appear, i meant we will start the process of building one and putting it in place asap
Possible candidates. Because we don’t have the ability to actually know. And it has to be habitable to humans, agriculture, and animal husbandry, which is much stricter than possible (bacteria) life.
As for using new planets for further exploration, it’s possible but will take time to develop the industry (while trying to build your new planet) and watch space for new targets.
