My understanding was that headrests were not actually for resting your head on, but just to protect your neck in an accident. They prevent your head from being flung backwards too far and potentially damaging your spine.

I don't have headrests in my Mog but do in my MG. In normal driving my head is nowhere near them

"Y mae dafad ddu ym mhob praidd"
1972 4/4, 1981 MGBGT, 1984 FLHT1340, 1980 XLH1000, 1990 ZX10