An indexed view serves a different purpose than a table. Also - if there is no table, then there can be no view.
A table is for storing actual data.
A view can be used for presenting data from tables in a user-friendly manner, for instance by replacing foreign key values that are substitute keys, with the natural key or a full name from the lookup table, or by adding user-friendly aliases for column names.
A view can be used to hide sensitive or irrelevant information for specific users. You can grant users permissions on the view, and not on the table, so the hidden information is truly inaccessible to them.
A view can be used to 'pre-process' joins, making life easier when you create queries - you don't have to set up the joins between the underlying tables again and again.
A view is the only object in SQL Server where you can create a single index that covers columns from more than one table. This is useful for queries where you have criteria spread over multiple tables.
I don't think there is much point in adding an index on a view if it covers a (set of) column(s) from only a single underlying table: such an index should already be defined on the table.
