Date functions like GETDATE() and SYSUTCDATETIME() are folded by the optimizer.

foldable date functions.sql

SET NOCOUNT ON;
USE [tempdb];
GO

-- Try substituting GETDATE() for SYSUTCDATETIME() everywhere in this script 
-- and you will get the same results.

CREATE TABLE a_table (
	  an_integer	INT		DEFAULT (1)
	, a_string	CHAR(10)	DEFAULT ('ohmigodwut')
	, a_datetime	DATETIME2(7)	DEFAULT (SYSUTCDATETIME())
);

INSERT INTO a_table
DEFAULT VALUES;

GO

-- Use the power of exponential growth.
-- This is the fastest way to create a massive table *from nothing*.
-- Number of rows created will be 2^x, where x is the number after the GO.
INSERT INTO a_table (an_integer)
SELECT an_integer
FROM a_table;

GO 25 -- This will produce >33 million rows, enough to let a few seconds pass while we populate or update this table.

UPDATE a_table
SET a_datetime = SYSUTCDATETIME();

-- the SYSUTCDATETIME() above is folded by the optimizer
SELECT DISTINCT a_datetime
FROM a_table;

DECLARE @start DATETIME2 = SYSUTCDATETIME();

-- insert a large number of rows at once
INSERT INTO a_table (an_integer)
SELECT an_integer
FROM a_table;

DECLARE @finish DATETIME2 = SYSUTCDATETIME();

-- it took many seconds to insert them, right?
SELECT DATEDIFF(SECOND, @start, @finish) AS insert_duration_s;

-- functions called by DEFAULTs are also folded
-- otherwise, you'd expect more than two values below
SELECT DISTINCT a_datetime
FROM a_table;

DROP TABLE a_table;