Why would VAs that have many memorable lead roles take lesser roles?
Recently, voice actor has been idle reduction.
So, maybe television stations and offices is made to use the young voice actor.  

----- Postscript -----
Although it is not a story that was only to Noto's,
in Japan, as the number of years that has been active as a voice actor is longer,
rank increases and salary will be higher.
So that, the request side want to reduce the production costs,
want to aggressively hired short activities years young.  

It also is might cause.