I think a lot of people sign up cause guns are cool.
in all seriousness, you get paid to raz around the countryside in 70 tons of armour plated badassness, or buzz around the air in an apache smiting the sh*t out of sh*t.
the army pay for you to do stuff we would all enjoy, rolling around in the mud, racing bikes, kayaking, climbing, and playing with otherpeoples hardware and not having to pay for it if you break it.
whats not to like?...
...well it depends if you can put up with the fact that at the end of the day, the army arn't paid for the fun bits, thier paid to kill people. (sure they avoid it where at all possible, and peacekeeping is better, but ultimatly thats what an army does isnt it? Kills the crap out of the other army till they quit and run away?)
i was aiming for RAF officer training, and just never got my arse in gear.
my choice (to go for it, even though i didnt) was based on getting to play with hardware (i wanted to fly heavy transport when i was younger), not worrying that ide have to use it to help my colleagues kill people