'Casual' means no tie as far as I'm concerned. What on earth would you regard as formal?
Since you ask, my wardrobe includes a dark DJ suit, dress shirt, bow tie and cummerbund. It also includes a white tuxedo jacket for tropical climes, and a selection of dark and light coloured business suits. All of these are kept for formal occasions. 'Casual' dress for many of my generation can sometimes include the wearing of a tie with say a blazer or corduroy jacket, sometimes not. Depends on the occasion and the temperature, I will never suffer discomfort for the sake of pointless habit or convention.
What I do NOT regard as 'smart casual' attire are blue jeans (these are irredeemably working clothes, which I garden in), 'T' shirts or polo shirts. I am sure that opinions will differ widely here, it's mainly an age-related thing.