Why would who want to? I consider each of the participants below. But first let me answer generally:
Why? Because it's right to. If you create good karma, the world will get better. If you do bad things, the world and your world (ie, your karma) will get worse. Paying for software you use extensively is good karma. Not doing so is bad karma that erodes the world (and your world), because it severs the exchange of value and erodes the justice that arises from that, which then reflects back on you inevitably.
For the participants in this archetypal case:
Apple - because it's not right to not pay the developers of software you use a lot, even if it was released under permissive licenses. Apple paying rsync producers for their software is just and right. Apple wants to be a good company, so they want to do this, too. Plus they could get a tailored custom license that works for them, and gives them standard good rsync.
The rsync developers - so they get the just reward for the value they produce, as is right and absolutely correct. They can choose to allocate that however they want, which is them expressing their good interest. What's good for them, is good for what they produce. Everything gets better. Happy cycle.
Everybody else - to participate in that just and right exchange of value, which nourishes the good of both the software, the developers, Apple, and everybody else, supporting the karma of the world, rather than participating in an exploitative abuse that erodes it.
More generally, using software extensively that is permissively licensed is not piracy, but it has the effect of piracy in that value consumed is severed from value rewarded to the producers. This is fundamentally exploitative and abusive, in the limit leads to poor software quality by eroding productive capacity.
One caveat is large well-organized ad-hocracies that maintain giant FOSS projects, like the FOSS or FOSS-like Linux distributions. These are sort of hybrid volunteer, corporate volunteer forces that are large enough to make such fossonomics work. But there's plenty of hyperuseful software built by tiny, single-person or single-company teams for whom those economies don't work as they don't have that scale nor fractional-corp-labor.
To conclude: normalize improving the world and spreading good karma by normalizing paying for the software you use. Even if a given developer team is yet to realize how to bank the value they created for you, as a savvy and responsible software consumer it's your responsibility to seek out and initiate opportunities to pay them, and not to seek out what you can take and exploit. If they make payment available, use it.
Basically, it's fairly simple. Don't be evil. And respond to and create opportunities to do good!
The rsync project has set a higher price than Apple seems willing to pay: allow users to run whatever they'd like on the hardware they've bought. Apple is free to pay that price and use rsync, but chooses not to
That’s a funny way to look at it, but that’s not a price that’s a policy. It doesn’t have the freedom from obligation that an exchange on price does.
Though I totally get what you mean and license terms are part of the cost that’s why a commercial offering with terms that can be negotiated and a price set to compensate for that seems a great option enough slack to capture the value for both sides.
