On 18th of June, Tom Lane committed patch: Implement UPDATE tab SET (col1,col2,...) = (SELECT ...), ... This SQL-standard feature allows a sub-SELECT yielding multiple columns (but only one row) to be used to compute the new values of several columns to be updated. ...

Every so often you might need to find a value regardless of which column it's in. Of course not in application code, as this would be very slow. But you might be in situation where you just don't know where did ...