Bravado, like most people. You'll be amazed how many people brag about sexual encounters and things they've either done or want to do but when the opportunity is dished up on a plate they **** out. This comes from personal experience. Blokes are the worst, full of themselves but when faced with the real prospect of a threesome or foresome they **** their pants.
Only a latent homosexualist would want to be in the same room as another mans erect penis, sorry , but it had to be said