Oh look, you uncloaked to hit someone, and someone else attacked you.
Oh look, all those random AOEs flying around just knocked out out of stealth.
Oh look, you were just seen from 20m away and attacked.
You are now in combat and can't leave until the other person dies, or it has been like 20 seconds. Good luck doing tons of damage while you are unstealthed though.
If an Operative is not unstealthed more than he is stealthed, the enemy team is bad, or the Operative is not contributing to the win (Cherry Picking).