Maybe people become teachers for the wrong reason. The go through college, study a few things they're kind of interested in, and can't figure out what to do. They decide to become teachers. After all, they don't have to become "experts" in any one field. They can simply learn a little bit about a lot of stuff, and stand in front of a captive audience repeating it over and over again throughout their careers.
This may sound a bit harsh, but study after study has shown that it's true. When asked in secret, on anonymous surveys, many teachers report that they got into it because they can have their summers of. Once they work at a school for a while, and learn that it's nearly impossible to get fired, this makes it even better.
This isn't to say that there aren't many very gifted teachers out there who do their jobs out of an honest love for kids and a genuine desire to see them succeed. There are plenty of teachers just like this. But even for them, their jobs are extremely frustrating. There endless amounts of red tape they've got to face, all kinds of budget constraints, and classrooms full of kids that would rather be anywhere than at school.
Sure, the rewards can be enormous. Seeing a kid who succeeds can truly lift your spirits. But to be honest, those kids are few and far between. Most kids go through school and just barely do enough work to get by. They do enough work to avoid getting into any kind of trouble and calling attention to themselves, but they don't ever truly exceed.
If you are thinking of going into teaching, make sure you are going into it for the right reasons. If you truly love to help kids, and are willing to work, really work, to succeed, and not get any thanks, then teaching is for you. If you are looking for respect, admiration, popularity, and more than enough money to survive, then you should probably go into another profession.
Sure, getting a job as a teacher can be relatively easy compared to other professions, but you've got a lot of headaches to deal with. Endless amounts of paperwork. Low salary. Terrible working conditions, complete and utter lack of respect from many of your students.
But if you truly want to make a difference in the world, and make a lasting contribution to society that will resonate for generations, then there's not better job.