Sweets left Bones because the actor John Francis Daley, who played Sweets, wanted time off to direct a movie.
The character of Dr. Lance Sweets was killed off in the season 10 premiere of Bones because John Francis Daley, the actor who portrayed him, requested time off from the show to direct the film Vacation. Stephen Nathan, the executive producer of Bones, expressed concerns that Daley's absence might be too prolonged, especially if the directing opportunity led to additional projects. This ultimately led to the decision to write Sweets out of the show by killing him off. The producers felt a prolonged absence of the character would negatively impact the show's continuity.
Therefore, Sweets' departure was due to a practical decision made by the show's producers in response to Daley's career aspirations and their need to maintain the show's narrative integrity.
