Linux won't be "the best platform" as long as everything that runs on it is cross-platform stuff. Linux needs a native toolkit, one that wastes no time or effort on cross-platform features. Qt will always be hamstrung by Troll Tech's commercial interests in shipping a cross-platform toolkit.
And if your program would be GPL anyway it's not an encumberance.
But it wouldn't be. I have written lots of different software under lots of different licenses. A toolkit that forces me to make everything either GPL or proprietary is a non-starter.
Remember Qt is not only C++ but actually pushes that to the extent that it needs a separate preprocessor.
Yes, that alone is a good reason not to use it.