I do. I mean, they're still significantly cheaper than SSDs. SSDs provide fantastic random-access time, but you don't need that for everything. I have an SSD for several of the drives in my system, sure, but use a rotational drive to store movies. No real benefit to random access if you're watching a movie.
Of course. Storage space is cheaper on 7200rpm drives, and has, historically, for years. SSD is rapidly dropping in price, but it's not on the same level, yet. Western Digital Gold 4TB is $150 USD. Crucial MX500 4TB SSD is $200.
EDIT: SSD is also not available for large drives, 8-20TB.
6TB drive really isn't a fair example, as hard drive sizes increase smaller drives aren't produced as much if at all. That has an effect of raising the price of the remaining small drives as your customer base becomes people who need that drive like if you have a drive go bad in a raid array and want a matching drive.