It's all a balance of safety and authenticity the value of which is different for every owner. My car came with headrests, and I'm sure glad it did. There's a strong reason to have them from a safety standpoint. Just do an internet search for "headrest safety" or related and you'll come up with a large amount of justification for them.
As for authenticity, that's another story. Some value authenticity far more than safety. If the car didn't have headrests, some owners would never consider it.
How and where you use your car might provide you with some direction. For me, in 21st century USA, three point seatbelts and headrests are the bare minimum of safety items I ask for, and my '69 is thus equipped.
Times change and so does safety perception. In 1987, you couldn't give airbags away here in the USA; there was all manner of "big daddy" and the "nanny state" telling us what to do and buyers were objecting. We actually got a great deal on a 1987 Ford because it HAD airbags and they couldn't sell it! Today, even removing the mandate for them, no auto manufacturer would dare offer a car without them. I think my car has eight of them, maybe ten...front, side, and even in the seatbelts. Frankly I wouldn't have it any other way. And no, they are not Takata.
