It places the value in escaping an engagement instead of winning it.
Furthermore, it discourages post T+60 action when the max landing bonus is had when RTBing from the primary mission.
Reading through this thread got me thinking about the whole point of scoring. It's a reward system, obviously. One of the things that we miss in a game is how pilots evolved in the war. They lived, they gained experience, they increased the potential of the team. The IJN had a serious problem near the end of the war, as an example, too many planes, not enough talented pilots. By attrition, the opposition got stronger and smarter, the IJN talent pool shrunk, and they continued to put greener and greener pilots up against real veterans gaining more and more experience shooting down the noobs.
I understand fully the desire to reward pilots for landing, to incentivize the drive to get home alive is a good goal. In game, that simple measure doesn't translate into gaining an advantage for surviving yet another sortie, it's simply a point consideration and Devil is right, it can be an incentive to avoid the fight. In a fight based event, you can't have an incentive to avoid engagement.
You could build into a scoring system a very real reward for surviving, while encouraging engagement. If you land successfully, good for you, you gained no kills, you get no points, being alive is a reward. If you get a kill, but are shot down, you gained something for the team but no longer translate that gain into experience as you died, so you get a point. However, if youou get a kill, and also survive, you gain for the team as well as experience and translate that into a landing bonus. You kill and land you get x2 points, or another multiplier. Bomber lives matter as well, getting your formation home gains more points than getting a single one home, you lost 2/3 of your fighting force, there were crews, pilots, gunners no longer bringing experience to the next battle so the landing bonus shrinks.
The more kills you get, and bring home, the better you score. Incentive to fight, incentive to get kills, huge incentive to get home. You even have a very solid incentive to get your ace pilots home, if you have no kills and he has 4, get his bellybutton home alive. There is a great incentive for the team to protect each other and work together. Keep the formations alive, keep the fighters alive, keep those who did the damage alive as the entire team benefits if those guys and gals get home.
You can use the scoring to do far more than simply generate points, you can use the scoring system to emulate real life conditions and simulate the experience gained by surviving a battle that only achieves a reward if you damage the other side. Never add a point bonus that rewards nothing.
The T+60 element is now a major factor, because of the ability to get another mission up and honestly have a shot at getting back into the win column if you out fly the other side. Come back with a vengeance, wipe their side out, and the side that's behind can get the landing bonus and actually catch up. Incentives to keep going past the initial engagement. These all have to be considered in a design.
Simple peanut gallery observation. Of course, numbers and side balance is a different consideration all together, as is being discussed in the scenario thread and does apply to FSO as well.