Why?

No one should be forced to do anything they don't want to. Why would you think of that?

they should wear them if they want to

That would make no sense

just a dress?

They wouldn't be men

Only Scotsmen. 😂

Why ¿?

Nope

If their DOMME has them in training to get in touch with their feminine side or it is a reward for good obedience, then YES, why not?

https://www.quora.com/What-would-happen-if-men-and-women-were-forced-to-wear-the-opposite-gender-clothes-for-week

Only the Sissy ones.😂