Juries are directly instructed that they can make that exact assumption. Destroying evidence means the jury will assume it was damaging. So to bother doing so, the actual evidence is almost surely worse than what they would assume.
4.19 LOST OR DESTROYED EVIDENCE
If you find that the government intentionally [destroyed][failed to preserve] [insert description of evidence] that the government knew or should have known would be evidence in this case, you may infer, but are not required to infer, that this evidence was unfavorable to the government.
Juries are directly instructed that they can make that exact assumption. Destroying evidence means the jury will assume it was damaging. So to bother doing so, the actual evidence is almost surely worse than what they would assume.
https://www.ce9.uscourts.gov/jury-instructions/node/674