Re: The Doomsday Machine - why no photon torpodoes?
No, photon torpedoes were around since first season.
There's no good answer in-universe for why they didn't use them at all.
In the end, it's not important to the story, anyway; they wouldn't have worked.
“A life is like a garden. Perfect moments can be had, but not preserved, except in memory. LLAP” — Leonard Nimoy (1931-2015)