Why doesn’t this happen anymore

[stinkfish]

I remember in the past seeing the center snap the ball as soon as a defensive player jumped offsides so to get the 5 yard penalty. I don’t really see centers do that anymore. It’s like they won’t snap the ball until the predetermined snap count no matter what. Am I right on this? Or have you noticed it happening and I haven’t? Do they not coach that way anymore? And what happened to tackling. It seems like somewhere between pop Warner and NFL guys forget or aren’t coached to wrap someone up and make a proper tackle. Everyone goes for a knockout shot. Why? It drives me nuts watching a ball carrier just bounce off all of these tacklers.

[Phishfan]

The center doesn't need to snap the ball anymore. The old rule was the offense had to stay still even if the defender jumped, now any offensive lineman can move if the defender moves first and causes it.

As for tackling, blame the limited number of practices in pads with limited hitting. Hard to practice fundamental tackles if you don't have contact.

[Spider-Dan]

Yeah, during the NE-DET game there was a play where DET jumped on defense but got back before the snap (while the offense remained motionless), and the commentators noted that Belichick was furious because he teaches his players to immediately touch the defender if they jump, so as to ensure a defensive penalty.

As for tackling form, I think it has less to do with NFL players not getting enough practice (as I'm sure they still get plenty).
I think it has more to do with players growing up in an environment with media coverage like this.

I think the current ruleset will encourage defenders to do less headhunting for the Big Hit and more form tackle wrapping up.  At a certain basic level, wrapping an opponent up for a tackle is a defense against unnecessary roughness penalties (though as Clay Matthews can attest, it is not a perfect defense).

[DaLittle B]

I hate the tackling,throw a shoulder not wrapping up,going for the strip rather than tackle the guy,throw an arm at a guy B.S. trying to tackle a guy by so many of the players in today's NFL...One of my big football Pet peeves.

I think a sub plot agreeing with Phish and Spider here on what has been mentioned,(coach speak would say) They focus on tackling during training camp,then during the season they get 3 days of actual practice each week. Those practices focus on working the game plan of the upcoming opponent,and trying to fix problems in reads/techniques each week...Rather than basic tackling drills