It removes a possible wax layer to allow the moisture to enter the seed itself. Or you can carefully crack them between your teeth. Yes sounds strange but doing that is a fairly common procedure.
It shaves the seed wall, allowing water to penetrate easier and thus start the germination process. Are these bought seed or bag seed? Maybe just not viable seeds.
Good call on scraping the seed surface. Once you put them back in the paper towel and bag, keep it in a dark but WARM place. Heat helps them pop too.
I've always soaked mine in rain water for 24 hours and pre-crack them after. After precracking I place into a moist paper towel (4 sheets folded enough to fit and I squeeze almost all the water out of the rainsoaked paper towels) and put the ptowels in a paper plate covered in clear wrap sitting on a thin magazine (15-20 pages) on top of my cable box for heat and I have real good rates. Some seeds may not sprout due to being cold depending on origin and so on but try soaking them next time and most will sink by 24-36 hours
Hindu Kush from Seed boutique. The first 6 I dropped in water. 2 days later the taproot came out so I transplanted them to a dixie cup on the windowsill. 3 came up the other 3 disappeared. Transferred the remaining 3 to MH light but must have fried them or overwatered because in the morning they were had. Figured I try the other 4 the other way in a napkin. One came up in a couple of days but that one suffered an untimely demise also. Now my remaining 3 I planted one in dirt and left the last 2 in a napkin after scuffing the seeds. I guess my last resort is to try and crack with my teeth? Has anyone else ever had bad luck with this strain for I have never had problems before but this was to be my first Indiga grow Maybe thats why they were only $23 for 10.