It wasn't 20+ years ago, that was my bad (there were some anthrax cases in the 90s, but the high profile cases were in the 00's). There are cases of the USPS finding traces of anthrax in mail every 5 years, on average, probably more that we don't hear about. Most recent high profile case was in 2008.
Every package is also X-rayed for potential explosives because of a scare 20+ years ago -- and thankfully they continued to do so otherwise we'd have some dead due to pipe bombs.
People find it extremely reasonable. We have increased airport security now because of what happened 17 years ago and most people also find that reasonable.
Not to get off topic but...Or so we were told.
Today, __every__piece of USPS is scanned because of a handful of rogue letters 20+ yrs ago? No one unreasonable would find that reasonable.