[swarmee]

Modern cards normally have a different type of alteration. Many have been buffed with car wax (normally to remove scratches) that may degrade their surfaces over time.

The number of cards being exposed now is much less, but that may not be attributable to the number of cards still being altered. Some people who have closed their companies as a result of their being found out as card alterers have started selling in different locations (Dave Thorn Small Traditions >> PWCC >> Probstein). So they're less likely to be found since they're hiding in a bigger haystack.

BODA are volunteers, so their motivation and time may be different. Many of the alterations they've found recently have been of the patch swapping/foil adding/serial number adding kind. Basically making a printer's scrap into a 1/1 card and getting it past the TPGs or making a 1991 Topps into a Desert Shield and getting it slabbed.