In SQL injection why don’t we use OR 1 or OR 2>1 instead of OR 1=1?

I read everywhere regarding SQL injection where it is said that if SQL query is SELECT * FROM table_name where username=’xxxxx’ AND password =’xxxx’ and if you want to enter always true condition then you will have to use ‘OR 1=1– then the query will be SELECT * FROM table_name where username=”OR 1=1–‘ AND password =’xxxx’. The logic behind the SQL query is simple since OR 1=1 is always true that is why it has been executed. However 2>1, 3>2 will always be considered true but why don’t we use ‘OR 2>1,’OR 1 expression in SQL injection?