Doesn't seem like a big hassle to me, if you want to use a mouse and keyboard you plug your mouse and keyboard into the adapter (two USB connections, 2 seconds) and the USB adapter into the 360 USB port. Seems pretty simple to me.
I think you are just making excuses.
Sorry, but I'm not. Like I said, the problem isn't plugging it in (even though you have to buy an adapter), but setting up surfaces for the mouse / keyboard. Normally a console like the XBox360 is connected to the TV, and used from a couch, etc. If you set up a desk to use a keyboard / mouse as a controller, it defeats the purpose of it being a console and becomes a hassle to use unless you set up a permanent desk, in which case it becomes a crippled PC taking up room.
TBH most people who haven't had to do it for any length of time overestimate the difficulty of using dual analog sticks. It feels wierd at first and takes some getting used to, but after a while it just comes naturally. This is very similar actually to when I started using a keyboard and mouse which felt so strage the first time I played my first FPS.
Of course, you can aim fairly precisely with an analog stick, but it doesn't even come close to the efficiency, precision, and speed of a mouse. For example with a mouse in an FPS, I can rotate 180 degrees and aim for a 20 pixel diameter area easily in less than half a second. In a RTS, the advantages are even more obvious, as you can select and command units very quickly if you're good with the mouse.