Remember whenever you compare the pro rules to high school rules that the pros have heavily skewed the rules in favor of the offense. Defensive battles don't keep viewers and seeing as the networks are the ones underwriting a major chunk of the league, what they want (high-scoring games) goes.
They tend to make things more equal in the high school ranks:
OPI - 15 yards and loss of down
DPI - 15 yards and automatic first down.
Offensive players know their routes, and are not allowed to intiate contact with the defenders at all downfield until the pass has been caught or otherwise touched. They know this. Their coaches teach them to hide the little shoves that provide just enough separation so they can get a reception unhindered. Their coaches are also the ones designing the "pick" play, putting the play in the team's playbook, calling for the play to be run, and hoping the officials are napping during the pick.
I don't know. Fifteen yards and a loss of down seems pretty equitable to me after they spent all that effort to circumvent the rules.