Sorry, but no matter what the travel agent said, at least 90 percent of the male passengers wore tuxes on formal nights on the QM2, and I was the only passenger (aside from children) not in a tux on the formal night on the Caronia. I was wearing a black Calvin Klein suit, but I still felt like I stood out like a sore thumb.
So, no, a tuxedo is not mandatory , but who wants to look like they can't handle wearing one? If you're dealing with a lot of attire already, what's one more hanger?
As for daytime clothing, I don't know what cruise your travel agent was on, but work-out clothes were definitely NOT the norm. Country-club casual is more like it.
I think this travel agent is being very misleading.