Because in our solar system, they happened from highly specific events (e.g. Jupiter traveling towards the center of the solar system, rather than staying out near the middle… but only for a little while, then returning to its standard position as a gravitational shield for earth.) We just don’t see evidence of that, let alone even seeing solar systems with planets of a varied-enough size to even theoretically support the CHANCE of it happening.

And that’s besides things we don’t have comparative evidence for, but which took ages on earth. It took a seriously long time for multicellular life to pop up. Easily could be a great filter. We also need tides. Another filter. We also need a planet rotating and orbiting at the right rates. Another filter. Etc.