The immune system destroy all the DNA in unexpected places in case it's a https://en.wikipedia.org/wiki/Viroid or something. Better safe than sorry.
One of the important steps in mRNA vaccines was to surround the mRNA with a lipid to ensure it can survive long enough to enter a cell. Naked mRNA would not have worked.
Not just rna, but dna as well.
One has to wonder whether destroy is all it does though. Analyzing this as cues about the surroundings seems like it could be pretty useful for successful living, and something evolution could well pick up on. Will we find eventually that some of those nucleic acid fragments were being hauled off for identification in something like an extra inner sense of smell?