This thread is bizarro land sometimes. TV is where it's at these days. That's why a lot of previously film only people are taking major roles in TV now. It doesn't have the negative stigma that it used to while providing a steady paycheck for several years.
But there is
a lot of TV on now. So chances your favorite actor that you don't see anymore is probably a series regular right now on a show and you had no idea.
Case in point:
Literally every cast-member on Lost seems to have disappeared into the ether apart from Evangeline Lilly.
The vast majority of the main cast from LOST has been getting regular work in series that have lasted multiple years:
Jorge Garcia: Hawaii 5-0 65 episodes
Josh Holloway Colony 20 episodes (One season of Intelligence before that)
Yunjin Kim Mistresses 52 episodes
Naveen Andrews OuaT 13 episodes/ Sense8 2 seasons
Daniel Dae Kim Hawaii 5-0 7 seasons
Emilie de Ravin OuaT 106 episodes
Michael Emerson Person of Interest 100+ episodes
Henry Ian Cusick The 100 53 episodes
Elizabeth Mitchell V (1 Season), Revolution (2 Seasons), etc
Ken Leung The Night Shift 3 seasons
Basically the entire cast has done really damn well for themselves and gets regular work That's huge in Hollywood. Only Matthew Fox and Dominic Monaghan haven't done much and I don't know if there are specific reasons in both of those cases.