Why can't we grow beards?

Regs....thats why....

Beards cause many problems in the health department. Clean appearance, taking care of a beard takes more time than keeping a shaved face, I know I now have a beard and it takes more to keep it looking nice.

Making the statement that "other nations allow it" does nothing for your argument. In fact it reeks of "Johnny jumps off the bridge, I must do so as well"!
Grooming standards are grooming standards. You signed the paper, you volunteered, you follow the standards. That's it.
I served when facial hair was allowed in the sea going services, then it wasn't. Guess what? I shaved. I didn't really like it, but the alternative was not acceptable to me.
Bottom line, you cannot have a beard because it isn't allowed.

I don't see a reason not too as long as it's kept in a neat appearance and doesn't hinder the NBC mask.

The reason the Army doesn't allow beards is that they prevent the protective mask from properly sealing. Think that's bogus? The reason Hitler wore that little clipped mustache was because in WW I he wore a handle-bar mustache like many others on both sides. When his unit was attacked with a chemical agent he tried to don his protective mask. Because of his mustache the mask couldn't be properly sealed, as a result he spent months in hospital while doctors tried to save his lungs. He clipped his mustache so he would never have the problem again; he kept it clipped as a reminder of what he had gone through.

I thought the military was very picky these days. Dont know about the Army, but in the navy,on board ship. You better be clean shaven enough to make a great air tight seal for your fire fighting SCBA,or your going to be breathing in alot of toxic smoke. And i hope your NBC mask is nice and air tight also. Id hate to hear about any of my fellow brothers and sisters getting a lungs worth of mustard gas.

because the generals' wife does not like it

What really surprises me is that most of the comments are from Army folks. When I was in the Navy beards were allowed it wasn't until the late 1980's they got rid of them. It was totally a political decision so someone in the upper brass and add some additional useless paper to their record to try and impress themselves and others. We didn't look like rabble, the beards I saw were always neat and well groomed and added to the esprit de corps. It was something that made the Navy standout from the other services. I saved a lot of money on razor blades for a while.

Our military is more impressive when it shows signs of discipline and physical standards. A beard can be well-maintained and impressive, but to my observation, most are not, fine in a civilian, unacceptable in a serviceman. I have seen members of foreign services in beards and my impression of them has been that they are inferior to Americans. Call that prejudice if you will, but most of the world operates on prejudices. If you must have a beard, find some other way to make a living.

The Navy already has that tradition locked down. Your more than welcome to join the Navy.