I do understand your reasoning, however if other homebrew developers had the same opinion they would have not implemented support for Gamecube controllers in their respective homewbrew applications. i.e. homebrew channel, many forwarder channels, etc. and those are not gameplay apps.
An advantage of using the GC controller is the lack of battery requirement for instance. Say that you would like to watch a movie and as you turn the Wii on you realise you have ran out of batteries in your controllers and do not have any spares. A GC controller would let you get into the Homebrew Channel and launch WiiMC to watch it. Otherwise you would have to either get out to buy more batteries or wait 3h to recharge some.
Is this an esential feature? Probably not.
Would it be useful? I believe so.
Again, do not get the wrong message. I am not demanding you this feature, but just suggesting it as I believe it could come in handy. 🙂