Why does selecting an attribute of an Oracle object require an alias?
Because Oracle made it so.
t_alias

t_alias
Specify a correlation name, which is an alias for the table, view,
materialized view, or subquery for evaluating the query. This alias is
required if the select list references any object type attributes or
object type methods. Correlation names are most often used in a
correlated query. Other references to the table, view, or materialized
view throughout the query must refer to this alias.