1 is the multiplicative identity, i.e. x * 1 = x, hence we can always leave out a "* 1" factor without changing things. A different factor, like 2, is more arb

1 is the multiplicative identity, i.e. x * 1 = x, hence we can always leave out a "* 1" factor without changing things. A different factor, like 2, is more arbitrary, since "* 2" can't be left out without changing the value. You can make the claim that a "* 1" factor is lurking in there, but even from that perspective it's less arbitrary than "* 2", since we could claim that "* 2" also has a "* 1" lurking in it, and so on :)