Probably many greedy reasons, but my personal favourite speculation: annexing Greenland surrounds Canada and stops any potential aid by its NATO allies in case of an invasion, since annexing Canada is one of the stated objectives of the US now.
In terms of strategy for actual national security, they already got all the access they wanted, if they wanted more all they had to do was ask. If they're the ones doing the attacking of a common ally, though, they wouldn't get that access. So it's only of added strategic value to annex instead of maintaining the alliance if the goal is to attack members of the alliance.
Very good post, I agree completely! It's easy to let perfect become the enemy of good.
One thing I'd add is that many social media companies sneakily get their trackers added to random web pages or other services you might use, so doing random things on the internet could be included as extra engagement (and it also doesn't require you to be signed up to their service in the first place, though it helps them). In this case their business is the data they collect on your behaviour, even outside of their own services, and the ads they can target to you using this on behalf of other entities who outsource their advertisements. It's quite scary how ubiquitous this is.
I think what OP suggested here is a very good mindset to live by, and it will help a lot. If you wanted to go one step further, you could consider combining this with steps to try and prevent these companies from still harvesting your data when you're not even aware that you're using them, e.g., by blocking such trackers as much as possible.