What Attacks a Virus?

I wonder to what extent this phenomenon of "defective interfering particles" explains the presence of quite a bit of retrovirus residues in the human genome.

One would think they'd get thrown out if they're harmful, or maybe even if neutral, but if having them there could soak up replication capacity for dangerous full-fledged viruses in circulation, that's a clear benefit in the short term. Millennia later, arguably maybe not so much benefit directly, but that could still be substantial generations to make other adaptations around the newly incorporated material.