How does a post that gets almost all of its facts wrong get modded up as Insightful? You started on a provably faulty premise, backed it up with inaccurate statements regarding WebGL, and then closed it out by saying something that I'd have hoped most of us here would trivially recognize as incorrect.
When you expect to get most of your revenue from selling apps in the iStore
Apple announced at the start of the year that they've paid out $25B to developers over the life of the App Store. Do some quick math, and that means that Apple is averaging $0.45B in revenue each quarter from the App Store, which would put it at <1% of their quarterly revenue (e.g. Apple posted $60B in revenue in their latest, post-Christmas quarter).
Which is to say, your basic premise here is that Apple is intentionally crippling the product that makes up 60% of their revenue (iOS hardware) in order to bolster the revenue in a segment that accounts for less than 1% of their revenue (App Store downloads). Seriously? Apple's main business isn't selling apps; it's selling selling devices that run apps, and you may even recall that back when the iPhone launched in 2007, the "apps" it supported were web apps, not native apps.
iPhone doesn't support WebGL for doing fancy 3D graphics on a web page
Could've fooled me. iOS 8 has been out for nearly a year at this point, and has had WebGL support from the beginning without any of the weird requirements you're talking about.
The browser actually DOES contain code for WebGL, but it's disabled...UNLESS your web site signs up to display Apple-provided advertising banners
A) You're confused. You're talking about iAds (and I'll discuss why I know you are in a sec), but the iAd advertising network only operates in iOS apps, not on websites. Sites can't sign up to it.
B) It's not disabled. See above. WebGL support was available as an experimental feature in iOS 7, and as a standard feature in iOS8. No ads or other funny business required.
The reason you're confused is because, technically speaking, iOS did have support for WebGL as far back as iOS 4.2, but it was only available to iAd developers. By that, I don't mean people who agreed to put iAds in their app. I mean people who were actually making the iAds themselves, since iAds are basically just mini webpages that display an ad.
If that seems a bit weird at first glance, recall that WebGL was a resource-intensive feature on the devices of that day, and Apple has a history of restricting the scope or operation of resource-intensive features until the implementations or device capabilities improve (see: background processing, native apps on Apple Watch, etc.), so it made sense at the time why WebGL was restricted to iAds, since they were designed to only be on the screen for short periods of time yet could stand to gain the most from such a feature.
The only sense in which what you said is correct is that for a few years the only people who were able to make use of WebGL on iOS were the ones making the ads, but it was never a feature that web developers had to make a Faustian pact with Apple to use. It simply wasn't available to them.
Safari uses the exact same core rending software ("WebKit") as Chrome - so it can trivially support everything that Chrome supports
They haven't both used "WebKit" since Google forked WebKit to create Blink over two years ago, but even before that, they weren't even running "the exact same core rendering software" for the last several years back when they were both running "WebKit".
Google and Apple have had divergent multi-process architectures for quite some time. Google built their multi-process architecture on top of the original WebKit (i.e. it's a part of Chromium, not WebKit), whereas Apple decided to bake the multi-process architecture directly into the rendering engine, which became WebKit2 and is at the core of Safari on iOS and OS X. Despite those differences, the two companies still tried to keep the engines in sync, but the difficulty in doing so (i.e. it wasn't trivial like you suggested) was one of the reasons why Google eventually decided to just fork WebKit and make Blink, since it wasn't worth their time.
I'm admittedly glossing over a lot of details since there's a lot of history here, but the long and short of it is that even when they were both running "the exact same core rendering software", they weren't actually running the exact same core rendering software, and it wasn't always trivial to port all of the changes back and forth. They both started from the same stuff, but it's been over five years since they diverged in major ways.
Any more faulty premises backed up by untruths you'd like to share?