But you're making quite a few assumptions. Your post is good because it has to be thrown out there now and then to remind us ALL who's game it is.
But since it's directed toward me, I just want to be clear, I'm a very positive coach because as I said above, I really don't care about winning and I'm passionate about development. I praise the heck out of the small successes by our weaker players and hold them accoutable only for lack of effort - not mistakes or lack of skill. I've worked with enough kids in multiple sports to know what 'joy' is in coaching and it has little to do with coaching talent or winning. It's just this (and knight58 nailed it too): Working with kids that want to get better. PERIOD. Note that there's nothing in there about talent.
But in the scheme of all this, consider the following little 'character check' I do daily: I do three hard sprints a practice calling them 'first period', 'second period', and 'third period'. They're tough (but only 15-20 seconds). Then we do one more...OPTIONAL 'Overtime' sprint. Guess who lines up and who doesn't? I'm not kidding. Noting also that I don't do any belittling or barking (or praising) for the girls that did or didn't skate it...it's just a daily opportunity for each girl to show their passion/heart/commitment to me AND to each other.
I'm not making it up that often the entire third line sits out the optional 'OT' skate and a first liner has never skipped it. You'd think the weaker players would be a little sheepish to skip the last 20 second skate given all the top players gut it out?? But they are not...obviously they are wired a little differently - they are great girls and I love them, but clearly their competitive fire and sense of team responsiblity is a few rungs lower. I find it interesting and enlightening.
Again, it's a small reward in the scheme of things to reward your most dedicated players with a few PPs. It's not hurting the development of my second and third line if I maybe shuffle the lineup once or twice a game because of a PP or if I call a timeout and let my top players lock down a playoff game. Like I said above...if anything, the other players SHOULD be thinking "I want to work hard so I'm on the ice for PP/pulled goalie situation."
Noting also that in past years, my top line generally got the LEAST amt of PP time because they were usually the ones on the ice working hard and creating situations that drew the penalty...then they sat on the bench while lines 2 and 3 skated the PP. So in fact the line that EARNED the PP was typically the one line that got very little PP time. And unlike your team, our second and third lines are not a meaningful threat to score on a PP - in fact, they often spend the time in our own DZ because the other team put out some top players to kill the penalty and it's a mismatch.
So, yeah...in practices, we do lots of small areas games/situations like you do and we're not working 'systems' or doing PP walkthrus, etc.... And we're trying to coach up our bottom and we do praise on them for small success, etc and ask only effort. We talk about each person contributing the 'small things' in practices and games and understanding that each short cut they take is a cheat to the team and the players who refuse to take a shortcuts. They all hear this but yet some don't line up for the OT skate? And will cut corners on pushups, etc if they think nobody is watching... (I do bust them on the pushups now and it does result in more resolve - resolve to do a better job of not getting caught!

And lastly, again, good general message in your post, but believe me, nobody will ever quit hockey because of me. My creed in coaching is that the kids should look forward to practices that are uptempo, challenging, and encouraging. I've never done a punishment skate (to a fault most say) or ripped them up for a loss or lackluster game.
So again, good points to remind us all...but don't throw these things out because I run a PP line once and while or call a timeout and put my best 5 or 6 players on the ice at the end of a game. In contrast, I know coaches who 'roll them' but do so much screaming the kids that often leave the ice or lockerroom in tears. And these coaches have no problem doling out heavy doses of punishment skates and belittlement to the point where kids don't want to be at the rink.
Again, I'm just sayin... Keep up the good work you are doing with the girls and your program. We're all learning.