SQL Server Management Studio Madness - why do I have to have scripts as strings?

What do you think the following option in the SQL Server Management Studio does?

Now one side of my brain says that I'll get a some preamble on my script looking a little bit like

IF NOT EXISTS (SELECT * FROM sys.views WHERE object_id = OBJECT_ID(N'[dbo].[SomeTable]'))

Well you'd be right! Well in the main.

Without the option:

/****** Object:  Table [dbo].[SomeTable]    Script Date: 08/28/2008 09:03:29 ******/
CREATE TABLE [dbo].[SomeTable](
    [Column1] [nchar](10) NULL,
    [Column2] [nchar](10) NULL
) ON [PRIMARY]

And with the option:

/****** Object:  Table [dbo].[SomeTable]    Script Date: 08/28/2008 09:03:49 ******/
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[SomeTable]') AND type in (N'U'))
BEGIN
CREATE TABLE [dbo].[SomeTable](
    [Column1] [nchar](10) NULL,
    [Column2] [nchar](10) NULL
) ON [PRIMARY]
END

But for stored procedures?

Without the option:

/****** Object:  StoredProcedure [dbo].[DoIt]    Script Date: 08/28/2008 09:10:53 ******/
create procedure [dbo].[DoIt]
as 
    select * 
    from SomeTable
    where Column1 = 'blah'
    

With the option:

/****** Object:  StoredProcedure [dbo].[DoIt]    Script Date: 08/28/2008 09:10:35 ******/
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[DoIt]') AND type in (N'P', N'PC'))
BEGIN
EXEC dbo.sp_executesql @statement = N'create procedure [dbo].[DoIt]
as 
    select * 
    from SomeTable
    where Column1 = ''blah''
    ' 
END

What I want to know is why does the 'IF NOT EXISITS' check require me to generate a script as a string invocation of sp_executesql?