[GENERAL] Any reasons for 'DO' statement not returning result?

[Xtra Coder]

Hi,

I'm just curious about the reasons of the design of 'DO' statement so that
it is not able to return result of the SELECT in its body.

References:
    https://www.postgresql.org/docs/current/static/sql-do.html

http://stackoverflow.com/questions/14652477/how-to-perform-a-select-query-in-a-do-block

With some former experience with MsSQL server, where 'complex' script is
executed easily and straightforward without any 'wrapping', like this
dummy-one ...

    DECLARE @a int;
    DECLARE @b int;
    ...
    select @a + @b as "a+b"

... every time I need to execute some one-time-through-away complex code in
PostgreSQL which returns rowset I'm disappointed - this has to be wrapped
into normal 'temp' function which I have to delete all the time in current
session, thus making an anonymous 'DO' statement use-less in 95% of my
use-cases.

So ... may someone know good reasons for such inconvenient design of 'DO'
statement?

Thanks.