Because the Operative isn't Rambo or Superman, he's a human like every other class. His job is to sabotage, perform reconnaissance and pick off stragglers. Now put yourself in this situation, 2 or 3 baddies are behind a wall waiting to ambush your team, you see all of them because you are in a flanking position, you could try and kill them, likely resulting in your death, or you could place a homing beacon on all 3 and notify your team of their presence. resulting likely, in assist XP for you, and a further push towards a main objective. (if you see any person alone, that isn't a heavy, all I see is a free interrogation, especially since i'm going to be one of two operatives on a team working together.)
Getting XP for beacon assist is a grand idea.
Also from new Rahdo interview:
Operatives get several unique death-dealing weapons, they learn how to hack into enemy communication channels to keep track of their location, and can even firewall Command Posts to protect them from the enemy.
Several unique death dealing weapons stop teasing us=> sadly this re-enforces the uber ninja lonewolf stereotype.
Hack communication maybe there will be comm towers
Firewalling I have mentioned before