For the good of the engine maybe. For the good of the driver... when you're finished scraping off it's better inside. Plus the windows kinda warmed up so it's easier to scrape.

Not sure what is the assumption. I have the opportunity to scrape the ice off of the car many times a year.

Depends on the weather. There were a multiple times when the running engine heating up the windshield was the necessary prerequisite to scrape the ice off.

I've definitely had a serious enough layer of ice on the windshield that my nice scraper was an exercise in futility. Maybe 2-3 times a year, but it's a thing.

Its just that I care more about my comfort than wear on the engine