Checking if Database Table exists

I read the wordpress codex and professional wordpress. It seems both use something like

if($wpdb->get_var("SHOW TABLES LIKE '$table_name'") != $table_name) {

to determine if the table exists. Is there any reason why CREATE TABLE IF NOT EXISTS ( ... ) is not used? It will check and create the table in 1 query, won’t it be better? Or am I missing something?

If you use “IF NOT EXISTS” then the dbdelta script will not upgrade your database with delta’s appeared after the initial creation of the database.

(assuming you want to re-use the same sql script)

at least… that is what i think