Oh wait! It doesn't show up when using the App Store app!
So even if you put a link there you need someone to be aware that such a link exists, to believe there might be something useful at the end of that link (which you point out, there rarely is), then wants to go to/turn on their computer, fire up iTunes, attempt to & succeed at finding your app, click the link, possibly register for your bug tracker (doesn't seem too uncommon), possibly check their email to confirm their registration and then finally file a bug report.
Ah! Not being an IOS dev (or owner) I had no idea. What is the typically-wrong use of it? Could it be simply that the word "Support" is a bad one to use for most people? Can it be changed to "Help?"
Anybody can feel free to contact me about this via my profile here, I'd truly be interested in making this flow easier and I know how to write this stuff.
I've seen a (large) number which just send you to the root page for the app (or company. or blog. or worse). Often without any clear way to send an email or report a problem, just a splash page that prompts you to download the app... which you've evidently downloaded.
Personally, a "report a problem" link would be a lot more inviting, especially if it let you send them a message from the app store, and include the last crash report (if it was the last one).
Oh wait -- they do! It's just a shame that most developers don't put anything really useful in there.:(