If I worked for VISA's marketing team I'd want to spread FUD like this and "XX% of dollar bills have cocaine on them; protect your children with a youth MasterCard!"
For those not familiar with using powered drugs nasally, a credit or debit card is also usually a part of the drug taking toolkit. Its one of those odd occasions when you need both cash and credit.
You usually keep the credit card though and not hand it to someone for a drink 5 minutes later.
Using banknotes is not advisable anyway. If you need to do this shit be smart about it.
There has been legitimate interest in putting RFID chips in high denomination Euro bills. It's not a whacky conspiracy theory but something actively being considered.
Honestly I would welcome it in all bills. Cash drawers could become self accounting, and bill sorters and talliers wouldn't have to rely on magneto optical sensing