Create view issues

Scenario : create user user1, user2
create table user1.table1 ...
create role role1 ...
grant select on user1.table1 to role1
grant role1 to user2

Test :
connect as user2
select * from user1.table1                -- result is OK
create view view1 as select * from user1.table1     -- return error --> no privilege

Why can not create view even user2 was granted select privilege on user1.table1 from role1 ?

But if
grant select on user1.table1 to user2             -- directly grant to user2
create view view1 as select * from user1.table1     -- result is OK

Please clarify me.

Thanks,
Rawee.