Despite "wasted" energy and possible risk to bystanders, having too much penetration is better than not having ENOUGH!
The now classic example is the 1986 FBI Miami shootout.
The 9mm HP met the FBI's required penetration standards, but tragically in that real world shootout, stopped just short of an instantly fatal wound. A deadly wound, but not instantly fatal. The shooter lived about another minute, and killed a couple of FBI agents and wounded several others in that short amount of time.
Many other things went hugely wrong for the FBI agents that day, but the blame was dropped on the 9mm not penetrating enough.
the FBI dropped the 9mm and changed their standards.
Interestingly enough, they have now gone back to the 9mm.
Police agencies have a legitimate concern over excessive penetration, especially in urban settings. A large city PD sees more shootings in a month than you or I will experience in a lifetime, so the odds of bystanders being hurt if much higher from overpenetration. (the odds of bystanders being shot by poor marksmanship seems even higher, but we'll ignore that, for now
)
I'll be blunt, I don't care what suits police use best. I'm not the police, and I have different concerns. I want two holes, so that, in the worst case, where the bullet didn't hit a vital spot, blood loss is faster. The sooner the brain loses blood pressure, the sooner things stop.
Having more than enough penetration to shoot through an attacker "front to back" means a much higher likelihood of having ENOUGH penetration when you have to shoot at an angle, when their arm is in the way, or through some kind of cover. Not a guarantee, there are none. But an increase in the odds in your favor.
Personally, I'm in a situation where I could use .30-06 AP ammo and the odds of endangering my neighbors are between slim and none, and Slim's out of town..
Most people aren't in that situation, and if you live in a crackerbox, surrounded by other crackerboxes in every direction (including up and down), your choices should be different than mine.
Until someone comes up with a defensive bullet that holds together while passing through, then turns to dust the instant it exits an attacker, you're going to have to make compromises between enough penetration to do the job under all possible conditions and something that might not.