Because they are not just BCAAs, but also include EAAs - hence making them great for the fasted training crowd - and minerals to support hydration, which is great for everybody. They don't try to woo you with bogus ratios of BCAAs: they are 2:1:1, but with a nice hefty dose of the leucine that matters.
Plus, they taste great and strong, so you can add a lot of water and still have a great tasting beverage to sip all along your workout, or anytime (sipping BCAAs between meals got popular for the cutting crowd too, and with the added EAAs you cover your bases). In summary: my go-to BCAAs.