Tom
Usually either "Gay" or not confident about their "manhood" and feel a need to "Show off"
prime
No it is not inappropriate for men to wear speedos. Swim briefs are the best sort of swimwear for men as they do not drag in the water, they dry quickly out of the water, and they give support where it is needed. Additionally if you wish to soak up the rays of the sun to develop your suntan then speedos allow this.
Anonymous
It IS weird if they think they're impressing women wearing a speedo. I've never know anyone who liked seeing that - sadly, for them, we mostly laughed amongst ourselves, shaking our heads like "Ew...what was he thinking" whenever we saw someone wearing one at the pool or beach.
Dr. D
If the man is muscular, ripping with muscles, then it's just okay.
John
Depends on their builds.