We are checked in security for our own safety and that of our families.
Just like bank robbers are kidnapping families so staff will open a safe, we could be used to bring items airside to be handed to someone else.
A good example of staff taking things through was the gun smuggling case recently in Atlanta where staff were using lax security for their own gain.
http://m.ajc.com/news/news/state-regional-govt-politics/atlanta-airport-boosting-security-following-gun-sm/njhxG/#__federated=1
For all we complain about Heathrow security, sterile should mean for all and include us, no matter how big our collective ego has become that we deem ourselves above checking.