Sim tray is different because you can replace it with firmware, whereas while Qi2 is great to have not everyone wants a physically large charger (I own a few of them). Design is about tradeoffs and having the USB-C charge port there is the right tradeoff as it gives people the opportunity to use anyone’s charger should they need to grab a charge, and everyone has one. Certainly far more than have wireless chargers. I’m not convinced by your reasoning, I’ve never had an iPhone port fail on me and I’ve seen iPhones survive extreme underwater tests on YouTube and keep my phone away from water nevertheless.One less “weaker point” for water and dust (while the phone is water resistant up to some depth for a certain amount of time, removing the port would only make it reduce risk for damage), for looks, for making more room for battery, while solid it can also get damaged when it’s plugged in and you hit the cable at an angle. If the saved space isn’t filled with more battery it gives more room for other stuff like maybe a speaker at the bottom or other stuff.
Same reasons Apple wanted to get rid of the sim card tray.