Guys, I got this. I will answer constructively.
1) While deployed, I worked between 12-16 hours a day on average. The typical "duty day" for a deployed Soldier, even at the lowest level, is probably 12 hours. When one is off duty in a combat zone, it's not like they can just go watch a movie, go shopping, etc. You walk back to your tiny little room, usually covered in dust, and you do what you can to enjoy your free time.
2) Training is conducted heavily in the months leading up to the deployment. Barring major changes to enemy tactics, being deployed is the time to conduct business, not train for it. There are also limited training areas and resources available as well. You don't replicate the vast training areas in a war zone, it's neither financially viable or available.
3) Video game consoles pack the largest amount of entertainment potential in one of the smallest, most reliable packages possible. Given the extreme environments, they are far more robust than the average laptop or tablet, so they are preferred entertainment devices. They also make it far easier to share media with friends and typically require less internet access to sustain than a laptop or other mobile device.
4) Speaking of internet, I was paying $90/month for 256Kbps access so that I could Facetime with my wife and kids back home. Think about that for a minute...yeah....
5) Reference the Taliban sneaking up statement, well, it's not like we're all sitting in our armored vehicles or at our guard post/tower playing Xbox. It's something done after you're off duty for the day and while the other guy who is working the other 12 hour shift is on duty.
6) When Soldiers get home they AREN'T walking all over the place in their uniforms. However, when we are flying home on commercial aircraft we typically get bused to the airport after a morning formation, so we don't usually have time to change out of our uniforms. Personally, I try NOT to fly in uniform as much as possible, but it's not always possible based on the timelines, baggage requirements, etc.
7) I suspect you might be seeing ROTC cadets or recruiters on your college campus. Or, maybe, if they have permission, it is a service member who works nearby and was granted permission to attend a class during their normal duty day. You aren't expecting them to change out of their uniform to attend a class during the day every time are you? Also, we certainly don't throw on our uniform just to go enroll.
8) As for the bums on the street question, it's a phenomenon everywhere in virtually every country with war veterans. All I will say is that we don't all come home in a healthy state and at the same time we've trained to give up all manner of civilized life to survive at times. Perhaps some of us choose to live the "survival life" in the streets as a backward coping mechanism. Some just aren't well emotionally, mentally, or even fiscally.