Here's some rational reasons for why it's a good idea:
* It would be a challenge, and (as there is lots of historical evidence for) innovation comes from people working on hard problems. So it would lead to innovations
* It would inspire a generation to be more interested in areas like science and technology
* The fresh start of a new planet would provide the opportunity for people to try out new forms of social structure. The founding of the USA is a historical example of this. Broken systems and structures is a big problem on earth right now.
* Ultimately if humanity only exist on a single planet, then it's at great risk of being wiped out by some catastrophe. Getting off earth is important for our future existence.
(A long time ago, I read Robert Zubrin's "The Case for Mars" and I think a lot of these ideas came from that. https://www.amazon.com/Case-Mars-Plan-Settle-Planet/dp/14516...)