40% of all Kickoffs have some kind of return. Think about about that on a per game basis... If there are 10 total per game (which is probably high), that means 4 have any kind of return, and the average return only gets the offense to start at the 21-22 yard line, so it actually hurts offensive field position. Add to that, the fact that statistically, KOs almost never get returned for a TD, so they aren't this game changing play you think they are. I wouldn't be opposed to keeping KOs for the opening play of the game and opening play of the half, but getting rid of them after scores.
Also, this shouldn't just be looked at as a safety issue; this should be viewed as progress in speeding these games up, fewer commercials, and increased ratings. Think about the the time between a team scoring a TD and the opposing team starting on offense. The team scores, the XP is kicked, they go to a 3 minute commercial break. They come back for the KO and then go to another 3 minute commercial break. I'd bet the whole process from TD to next offensive snap is close to 10-15 minutes of real time. If you eliminate one of those commercial breaks, that potentially reduces the time of a game by 30 minutes, assuming there are around 10 KOs per game.