Complexity is the strategy. If the rules sound uncertain enough, people keep asking. And if people keep asking, licensing fees keep flowing, even after the copyrights have expired. Confusion, after all, is far cheaper than litigation.
In other words, it's capable of doing a lot of people's jobs reasonably well.
,这一点在电影中也有详细论述
and further perpetuated by backwards compatibility.
$5.99/month for 12 months (save $5/month)