Why do scientists think that all forms of life on earth have a common origin?

There are several facts that linked life to a common origin such as:

Comparative anatomy, where different species have common traits. This includes homology and analogy, vestigial structures. Fossil record. Species distribution in different continents, some others.

I believe the most valuable evidence is that DNA is the molecule that carries information in all living things (eukaryotes and prokaryotes) even viruses contain either DNA o RNA. Is difficult to think that life started in different ways but then converged in the same kind of molecule to carry the information.