I think that may have been a sensible scripting decision after a few too many stories where we were meant to act surprised by the reveal that a man with a name like Master was in fact...the Master! Better to admit it straight off.
(David Macintee managed two brilliant twists on this in his books, one of which featured a guy called LeMaitre who was just a guy called Lemaitre, it's a name - and the other had the Master trading under a name which was an alias for Master in an alien language readers won't decipher)

A more recent example: there would surely have been enough trailer material in 'Bad Wolf' just from the reality TV with robot celebs that giving away the Dalek involvement in the teaser too was just baffling.