Yeah, there are so many movies based on media with a deeper and richer source material than can be presented well in a 2-hour movie format. For example, the Ender's Game novel spent a significant amount of time on the progression of Ender's career at the Battle School and the movie only spent as much time as was necessary to show that he was good. A TV series could tell the parallel story of Ender's Shadow as well in the same season.

A counterexample is that sometimes the TV series may over milk the source material and drag out which should be a shorter story. The first season of American Gods was awesome, but they kept dragging out the series way too much by stretching out the stories of minor characters and fumbled in the end.