Think what Guzzle is saying is that he is using the available technology in the way most convenient to him. I do pretty much the same, except for having my music on an SD card.
I don't disagree with that, each person has their own convenience... but it's how that person keeps up with technology v convenience. The 'physical' media format is dead, wether that be a HDD/SD/CD/DVD etc, the now (and future) is streaming via Apps, so that's what you'll get with ACP/AA etc. Apple/Google are not going to invest in making their software compatible with formats/ecosystems that have no compatibility or are dead, they simply provide an alternative which is equal or better. 
Not everyone is that bothered about keeping up with the latest technology. Especially while it's as half baked as App Connect in the Golf currently is.
If a version of it comes along that adds functionality without taking away some of the existing functionality of the built-in system, then I'll use it. But until then, for the odd few times I need to use nav, it just doesn't offer enough functionality in other areas for me to swap.
As for streaming, I spent a lot of money on my music collection. I have no intention of throwing it all in the bin and paying apple / Google / Spotify £10 per month to rent it back again. Nor do I want to give apple a grand, or whatever ludicrous price they charge these days for a phone that holds as much music as my iPod does. Hence I don't use Carplay.
You might think App Connect is the bees knees, but this is the internet, and occasionally you'll bump into someone who has a different opinion. Doesn't mean one of us is wrong, just means we see things differently.
That ok with you?
