Well apparently until recently David Beckham used kangaroo skin soccer boots. The Adidas Predator uses kangaroo leather apparently. Not sure what else it's used for.
The articles contradict each other. One of them says that if the size of the kangaroo market increases then we'll be in danger of making kangaroos extinct. Another says that kangaroo farming would be uneconomical and that it will never be a big industry. There are also laws on how many Kangaroos can currently be hunted and while one of the articles says that there is no way of checking to make sure these rules are enforced, the current figures suggest that about a quarter of the legal limit is met - so there shouldn't be any problems until the market is 4 times bigger - which would be uneconomical anyway.
You are right, if this was a genuine problem then people in Australia would campaign about it instead of about sheep, pigs and chickens.