Good point, but I think things were advanced enough that in the early 2000s they could extract DNA from objects sufficiently well to get a hit.It may be less that nobody considered it, but that until the advent of PCR it wasn't considered sensible to use consumptive (destructive) tests that may not reveal anything. By waiting, they have made a prudent choice. Far, far less material is required these days to get a profile, and profiles can be developed from degraded or mixed samples that wouldn't have been attempted a couple of decades ago.
MOO
I am so curious what it was that gave the DNA, hair, blood, saliva...may never know.
It's exactly this reason they are holding on to the 3 non rooted hairs kept in evidence for Sally Shepherd. From what I have read, we aren't anywhere near the level of doing anything with them.