There is something to be said of contact sports and the adrenaline that comes from engaging in them. While I'm not an adrenaline junky I do believe that such sports are useful on a physical and psychological level. While maybe not everyone's "cup of tea" I feel that putting them into your fitness activities can be helpful in the process of rounding out your personality and abilities.
The first think you can think of is the fitness side of it. Yes boxing specifically will get you into shape while much of the background work must be done at the gym. So it gives you a focus for your workouts. Getting better and stronger takes a level of commitment.
It is also a useful skill. While one should not walk around like they are a "god" among men it is a useful skill if one is attacked. We hope we live in a safe world but we sometimes come across physical intimidation by others who have not learned other ways of handling conflict in a non violent manner.
There is also the psychological aspect that comes with both fitness and the ability to defend oneself. There is higher inner confidence because you know you can hold your own. This is important in the way you talk, walk, think and engage with your environment. Confidence and arrogance are two different things and knowing the difference is important.
Ok...so the few stings of a practice beating with an opponent does sort of stink yet the overall benefits outweigh the few bruises you might receive. Learning against a bag is one thing but having a practice opponent is another. To get a feel for the weight of another person, seeing their movements, and preempting their attacks teaches body language skills.