Are the identities of these people known? So you know who the real person is? (Social media accounts, phone number etc.)
As far as I know, many people hang out here anonymously. As you said, even people who are 100% safe can make a lot of mistakes for bitcoin.
Escrow are usually members who have proved their integrity by doing various fair trades here.
It is based on a trust system.With time and continuous fair deals the get lots of positive trust (numbers shown in green below their username) making their account valuable.
For example if someone's account is worth 1 btc due to all good rep he has,he would obviously not scam anyone for say 0.5 btc.
This is not to say that he will cheat for more than 1 btc
The point here is that an escrow is safe for an amount his account is worth of.