It's not exactly the default assumption though. Historically the default is that life was magicked into existence or came here from a previous world or some oth

It's not exactly the default assumption though. Historically the default is that life was magicked into existence or came here from a previous world or some other creation story. The current abiogenisis story of molecules->proteins->cells->Life is relatively recent. The other thing is that because we have a fairly... ?linear record of evolution: if life did originate somewhere else it got to Earth in something like prokaryotic single cell form 3.5 billion years ago. Which means we can't use the idea of panspermia to tell us anything. It's neither predictive or explanatory. It tells us nothing of how or where life did originate or how life got started on Earth or what or where we should look for or expect in the rest of the Universe. The current theory suggests life could pop up extremely quickly, which itself already implies life is likely to exist in the rest of universe on some level so panspermia doesn't even mean anything with regards to how likely life is anywhere else.