Because once I know my playbook finding the play I want takes no time at all. Without accelerated clock I could easily run 125 offensive plays. Without acceleration I could easily be behind center with 30-35 seconds still on the clock, a no huddle offense without ever going no huddle. Hell, even with acceleration at 26 seconds I could still run a 100 plays if I wanted to.
My clock setting has had no effect on what the AI teams are doing that I have noticed. No huddle teams have run 90-ish plays against me. As for "clock draining teams"? I've never played an AI team that has "gone slow" (with the exception of 4th qtr lead), or if they did it was unnoticeable.
My accelerated clock takes it down to 26 seconds, hardly a small window when considering how quickly a user of the AI can or does call a play. IE neither team is running "up against the clock". If I'm nursing a lead and running clock in the 4th qtr it's not unusual to be at the LOS with all 26 seconds still on the play clock and then having to wait to snap the ball. Turning off accelerated clock would probably add at least 30 minutes of me just "waiting at the LOS" to the time it takes me to play a game.
All the while having no affect on the AI.