Presumably because they care so much about privacy being a human right, and every day This Page[0] exists it breaks their heart. Breaking ties with China would be a great way to start getting tough on autocratic privacy overreach.
Oh ok, that I understand completely. I see why there are compelling reasons for them to do so, but I didn't understand the language of "obligated" to do so. That made it sound like there's some formal obligation, legal or otherwise.
[0] https://support.apple.com/en-us/HT208351