Well, even if you can do something by hand, there's a market for a gadget that will do it more conveniently. There is a market for food processors and rice cookers. I don't think Juicero is a good example of "stupid money" craze. Theranos is.
Large eCommerce sites are constantly scraped by competitors, market research companies and even vendors (to ensure sellers honor MSRP). Scraping activity is usually throttled at reasonable levels.
Here's the difference - when shit hits the fan everyone in the room wants to solve the problem and they are actively helping each other. Technical interview is completely different.
The problem with take home assignments is that while investing time the candidate doesn't know how it will be judged. Sometimes people want just a working prototype but sometimes they want essentially a production quality high-performance code.
I don't get how IQ could be considered inherent. It's a test, so results are defined by talent and training. A person who spent a month solving the types of problems present in an IQ test will certainly get a higher score. By, the way, you did become better at coding by solving Leetcode problems, cause now you can easily spot them in the wild and use a proper algorithm instead of some naive solution.