The simplest answer is the one you are looking for. But if I devote an inordinate amount of time to the battery, team fielding suffers. If I devote too much time to that, hitting suffers. Too much time to that and we're out of sync on the bases. Again, without 4 hr practices, I can't cover everything I would like to cover.
I have been blessed to have P's that don't need large amounts of Team Practice so that they can throw. They realize that if they want to be the best, they are going to have to work outside of Team Practice. It's no different than their school work. If they want to excel, they have to work outside the classroom. Probably not a bad life lesson. Plus, they find time for Pitching the rest of the year without my help. They work it around Basketball, Volleyball, Cheerleading, homework, FFA, etc. So why is it any harder to find the time during the season?
As far as not working much before the first game, I don't care much about the first game/ week. Nobody in the history of softball has won a championship during the first week of the season. The end of our season is the important time. In normal years, I only have about 12 practices before the first game. Half of that may be inside. That's roughly 24 hours. In that 24 hours, I have to figure out who is on the V roster, who can play IF or OF, who can bunt, who can't hit, can I teach a big stick to catch a ball at 1B?, etc. You may think it's sacrilege, but I don't work on rundowns till we are about a month into the year. It's a situation that doesn't happen very often. If it does in the first few games, well, either we'll look real bad or the players will figure it out based on experience. But I can't prioritize the time for rundowns during my first month of the season. But that's just me. I'm willing to hear the experts in the stand tell me everything I'm doing wrong. Notice I said hear, not listen.
And to be fair to the HS coaches, most pitchers when left to their own devices will perform a workout that is "less than optimal" in terms of both intensity and duration. Starting with those idiotic wrist flips. It should not take that long if they focus and get it done.