The following comments are broadly true of the US military, but since the Army is the only branch I have firsthand experience with, the usual caveats apply. So take what comes below with as much salt as you like.
Here are good reasons for joining the Army: job training, money, always wanted to do it
And here are bad reasons for joining: travel, adventure, bragging rights
You can get excitement, a challenge, etc without agreeing to a multi-year commitment that might get you hurt or killed. Even being stuck in a miserable situation is something worth avoiding.
Popular entertainment often imply that the hardest parts of military life are combat (something relatively few experience) or the physical rigors of training (heavy exercise, lack of sleep, and so on). I was almost 31 when I joined, so my perspective on hardship was different.
There are many hoops to jump through in the Army, and no matter how many you get through, there always seems to be another one. That gets tiresome.
I expected petty harassment at basic training, so it didn't bother me. Then there was another round at DLI (Defense Language Institute), and more rounds at AIT (Advanced Individual Training) and BLC Basic Leader Course). All that happened by my third year in the Army. By that time, my patience for Army reindeer games was just about gone.
Despite all that, I'm glad I joined. Learning Arabic and meeting the Army's physical fitness standards is something I took a lot of pride in. And the money was pretty good too. The job I had at NSA through the Army also made the journey worthwhile. I got to see something very few people know much about.
The fun GI Joe stuff of basic training only lasts a few weeks unless you do a combat arms MOS (job) like infantry, armor, or artillery. Like other soldiers, those guys spend most of their time doing boring stuff like watching PowerPoint presentations or doing boring online classes.
Bottom line, if you join the military, be prepared to suffer. And remember that if you have a why, you can make do with any how.