If you're a professional, you're less likely to submit work you value to be used for free-- you may find other value in it being used but not being paid for its use runs counter to your status as a professional. If you're a normal everyday person then why not, it could be fun.
This is the point people keep missing. Apple could have commissioned pros to capture professional images using iPhone, and probably even used those photographers names as part of the promotion. Nikon, Canon, Sony all do this.
https://www.nikonusa.com/en/Learn-And-Explore/Nikon-Ambassadors/index.page
https://cpn.canon-europe.com/content/ambassadors/brent_stirton.do
https://imagingambassadors.sony.net
And Apple does make a point of naming the professional photographers that will be judging the photos.
Professional panache wasn't Apple's goal with the contest though. Apple's goal was to say "here's something someone like you submitted to our website".
This is also mostly true. Amateurs are probably harmed a bit because compensation means more professionals are likely to enter the mix reducing their chances of seeing their works around town-- but the world, on average, isn't much worse off. We're only talking about 10 people, after all.
This really is a lot of noise about the fate of 10 photographs.