[keycloak-user] What's the point of creating roles per realm and client?

I'm pretty new to keycloak. Amazing application btw. It's working very well, however I found strange/confusing that I have to create roles in the level of the realm, then per client and then assign to each user. What I mean is: why don't we have the roles created in the level of the realm and then we just assign per application user or is there an option to make that happen? Otherwise I have to keep creating roles for all clients, then assigning for all users. In my case there aren't many users/roles/applications, so it's fine. But it would be nice to know how to do that. Thanks Renann Prado