If you look at some of Hollywood’s trends, you can notice a pattern: they’re rehashing old movies. The writers have almost entirely abandoned the concept of new ideas, so the remakes and reboots come out one by one.
Iconic roles can usually be locked down to a single face. Indiana Jones will always be Harrison Ford, Luke Skywalker will always be Mark Hamill. There’s a certain special connection you can make between a character and an actor if they become one and the same. There’s loads of iconic roles that have been played by different actors, however.