Running is the #1 form of defense - you may never win, but hey, at least you'll never lose as long as you time your escape right.
Besides, the MA is full of planes that do over 350mph TAS at deck and the bases are placed on average 30miles away from each other. If people venture out at about 15miles and meet at the middle point, basically 1~2 minutes of running will get someone to homebase when they start to dive.
Even a La-7, the fastest non-perked plane, might not be enough to catch down its temporaries in time, if they turn around and dive full speed towards home. The most popular planes in the MA easily reach over 450mph at dives and then slow down and stabilize at speeds over 360~370mph typically. In about a minute or two it reaches home base, and more likely, within about 30 seconds it would be able to meet other friendlies to seek help.
So, when anybody can do this, why the hell should anyone expect any plane to actually fight? Its not cowardice, its not newbie stuff. It's basically the simplest, most rational choice of behavior - why risk a fight that might take minutes and has a considerable risk, when you can run for 30 seconds and reach home?
Not everyone is a serious flyer nor a combat buff. Expecting them to "honor" some imaginary code of "combat" and fight everytime you want a fight, is just plain stupid and selfish. Many MA gamers are casual/light gamers who don't necessarily share the same views on "fun", as you miserable, complaining "vets" gathered at this spot.
Besides, the terrains, the planeset, the basic system, etc etc.. everything is geared to make people act that way. Why, I don't recall any of the most vocal whiners here in this post ever supporting (for example) something like longer bases distances... perked latewar aircraft.. RPS.. or any other ideas that might have been able to stop people from acting this way.
Nope. Most of you here wanted furball friendly terrains, short bases distances (because flying a long time is boring), no perks for late-war vehicles (since it inhibits their own planes most of the times), and etc etc..
And after all that, contributing a very hefty, conservative public opinion that helped make AH MA stay as it always was - unchanging, stagnant, chaotic, unstructured - and now start to complain about people that don't fight anymore.
Basically, like it or not, you guys had it coming.
As long as the terrains, planes, and gameplay stay this way, people will always act this way. That's how the game is structured.