1. There's really no space for it, if you look at teardowns. So something took its place.
2. It does give better water resistance. Google the water resistance tests between iPhones and others. The difference is night and day in real world performance.
This guy was able to add the headphone jack back into an iPhone (https://www.youtube.com/watch?v=utfbE3_uAMA). The argument that there is really no space just isn't true.
2. No. Samsung phones are far more water resistant than iPhones are with a jack on it. I would love to see your links to said research.
Earbuds that work with the iPhone come in the box (and prior to the just announced models even an adapter was included). I'm not sure how lack of a jack pushes someone to buy AirPods. Maybe it makes them think about buying bluetooth headphones over wired if they were already thinking about third party headphones? Maybe.
Also while you may disagree about the 'barometric vent', it was put in the space that the headphone jack would have taken.
As pictured above, you can see a piece of plastic sits behind the ingress protection (waterproofing!), right where the headphone jack would have been. And (update!) according to Apple it's a "barometric vent." Apparently adding all the waterproofing to the iPhone 7 and 7 Plus meant that it was more of a sealed box, and so to be able to have an accurate and working barometer, Apple used that space. The barometer is the thing that allows a phone to measure altitude, and Apple points out that on the iPhone 7 it can measure even minor changes like climbing a flight of stairs.
https://www.theverge.com/2016/9/16/12941040/iphone-7-teardow...
Knowing my altitude is something I need on at least a weekly basis. I'm OK with losing a port I haven't used in a couple of decades.
And AirPods? If you keep them in the case between uses they should always be charged.
How are people being "pushed" to buy Airpods when they can use any Bluetooth headphone, the headphones that come bundled with the phone, or use their own headphones with a $9.99 adapter that they have included up until yesterday?
So, if your headphones don't support AAC, they will (most likely) fallback to SBC encoding with a subpar sound quality. Don't want a subpar sound quality? Buy Airpods. Or Beats. Or some other overpriced thing that understands AAC. There was some 100 year-old industry standard regarding sound transmission, but apparently it's "obsolete" now, because Apple said so. And bundled headphones don't sound too good.
The removal of headphone jack was purely a political decision to spite Qualcomm and screwing over Apple's customers.
But if you aren’t satisfied with the Apple wired headphones, up until the 12th Apple bundle an adapter, you could choose any wired headphones you wanted. After the 12” it would be $9.99. It’s still not forcing you to buy AirPods.
As far as Bluetooth, there are other non Apple/Beats Bluetooth AAC headphones. Nothing forcing anyone to buy them from Apple.
FWIW, my lack of headphone jack had nothing to do with me buying $170 airpods. The product sells itself. It literally felt like something out of the future when it launched. Opening and closing the lid makes me happy on a daily basis. I can't think of a better use for that $170. It's a product that is pure joy to use, and completely eliminates one of the biggest annoyance factor in my daily life: tangled headphones, and worse, that feeling on your ears when you accidentally tug earbuds that are in your ear. So frustrating!
Edit: Oh, and when I broke my older model with saltwater, they replaced it. Twice.