Because you're insane! That's why. Even when properly configured, the learning curve on being an effective stick pilot somewhat resembles Mount Everest with about 40,000 mouse aimers training their guns on you from all sides. Unless your the god of space combat sims (this is arcade mind you) you've pretty much resigned yourself to sucking your first dozen rounds, bouncing your target like a hot potato while you figure this crap out. Ok, you do have one advantage...

You kicked that damn instructor off your plane, preferably from about 4000 feet up. Even if you did the disable trick, he still won't let you pull 15G like the UFO your plane was always meant to be. Setting the controls to realistic is the magic button that will make you nigh unstoppable in a straight up turn fight. However, if it was that easy, the WT forums would be flooded with tears of the unskilled... uh, more so than usual. No, you still have to spend the next week and a half of your life figuring out the WT control settings and have the magic touch to keep that bouncing excuse of a $*#@-box you call a fighter on target.

I can't really help you with that last part as it comes from experience. I can do it with the benefit of about two decades of PC flight gaming. However, I can help with getting your head around that configuration part. So without further ado...

IMPORTANT: Set your camera smoothing to minimum. Otherwise in 1st person your crosshair is going to be bouncing all over the place.

1. You pretty much resigned yourself to never winning a head-on pass (unless you are in a Yak or beaufighter or the like). Seriously don't do it (not that you should even with mouse aim). It ain't worth it. Dance around the initial pass and use your knowledge of ACM to rip him a new one. Wait, whadda mean "what's ACM"? Well, in that case you're proper F---ed now are ya.

1B. Learn Air Combat maneuvering. Wiki it if you have to.

2. Exploit the vertical as much as possible. Immelmann, Split-S, High Yo-yo, Low Yo-yo, YOLO!... uhh... Point is, you can point your nose up or down at will more easily. They can't.

2B. Speaking of exploiting, exploit the arcade flight model as much as possible as well. The higher your speed the more you can break the FM over the mouse users (21Gs? no problem if Gaijin hasn't fixed the compression effect for the aircraft yet).

3. Each aircraft will preform differently, more so than with mouse aim. So it is even more critical that you learn their advantages and disadvantages (fly multiple nations. WT makes it easy and you will be better for it). Not all planes will achieve UFO greatness at high speeds. A few will start handling like a truck so learn em.

4. DO NOT, under any circumstances use 3rd person. 1st person (cockpit or no cockpit, your choice) gives you a better vantage for your guns anyway and it really helps to know where your nose is pointed.

5. If you want to extend this guide to a gamepad, do so at your own peril. The only thing worse than the ol' stick is shrinking down the movements of your entire hand to your thumb. Good luck with that.

6. Don't try to adjust your settings in the tutorial. It just bugs out. Complete the tutorial and then use free flight mode.

7. Here is the post in the WT forums containing my current config of the week. just import the settings through the controls options menu.
http://forum.warthunder.com/index.php?/topic/50769-how-not-to-suck-with-the-joystick-in-arcade-video/?p=714090

Note that you must log into the WT forums before the link will work. Also I've ♥♥♥♥♥♥ around with the default keybindings quite a bit.

8. Might I add that simplified controls are the only way to fly some of the Americans in historical (I'm looking at you kittyhawk)

9. Actually, I lied about not being able to help on the flying aspect. This is basic but really easy to overlook. Never pull more Gs then you absolutely have to. You will want to keep as much speed and/or altitude as possible so that you can use it to break the flight model later. Take your turns nice and easy when out of combat. This is especially critical for the Americans and it's another thing you can do better than the mouse user (The instructor uses too much rudder in it's turns).

10. Check my other guides as well. I go into more detail how each individual plane handles with the stick.

There's probably more but it escapes me at the moment... ah well.

This isn't even my best kill streak anymore. Just the one where I was recording at the time :D.