However, they are commonly used in games such as Half-Life or Call of Duty to bring in new enemies or challenges to the player in a seemingly surprising manner while they are still playing.
The intended results of this style of presentation is to increase immersion and to maintain a smooth-flowing experience that keeps the player's interest.
Resident Evil 4 has many examples of scripted sequences that utilize a quick time event to feature more action-packed game play.
Games such as Call of Duty have been criticized for their reliance on these sequences, as many feel they tend to guide a player through a game by the invisible hand of the developers, blocking progression with invisible walls until the scripted sequence has triggered further progression.
[1] Also, the use of scripted sequences may diminish replay value as the surprise effect is negated upon subsequent play-throughs.