All the best songs are in Ionian? Hmmm, for guitar freaks, how about Satriani's Flying in a Blue Dream... that's Lydian. For the more pop oriented crowd, Better Than Ezra's Desperately Wanting is in F Lydian. The chords are F, Am, G, C. Sure you could say that's in the key of C, but if you said to someone, we're going to jam in C, you start - would they play with a tonic of F? When you say, in the key of C, you imply that C is the focus of the progression. Do modes exist? It doesn't really matter... I mean, does the major scale itself exist? They're all just a convenient way to organize musical thoughts... the same with modes. If thinking in terms of modes doesn't work for you, don't. There aren't any strict rules on how you should think.