I think the mandatory aspect of it, even when commonly blown off, is important in some cases. There are lonely pastors in struggling congregations for whom a conference is like a much needed and deserved min-vacation, rejuvenation, and reconnection to colleagues and higher level theological discussion. But the congregation will not grant the paid time off or hotel/meal expenses unless the pastor, backed up by the DP, can point out that attendance is mandatory. It takes the guilt and awkwardness out of the equation. Obviously, if there is a funeral or something the pastor might have to miss the conference; it is excused. But if it just that the congregation doesn't feel like paying for it or giving the time off, the official rule becomes an important safeguard.