Well, for me it's mainly to keep my own fitness up and to have something different next to my standard running schedule (which is one day on-one day off). It seems a great way to keep the whole body in shape and in balance.
I'm not necesarily opposed to human versus human martial arts, but it has to have more of a philosophical basis for a healthy body and a healthy mind than that it is a way to be on the defence/offence in human encounters, like Krav Maga seems to be to me. I guess that is not really my thing.
There is a school in my town that teaches Wing Chun Kung fu, which sounds interesting, but on the site they do emphasise the human vs human aspect. However, I just found out that they offer trial-lessons so I'm definitely going to check that out.
I have to look around a bit more to know what is offered locally though.
Honestly, maybe something like cardio boxing might be ideal for you. With the healthy body healthy mind thing, you might wanna look into tai chi or aikido classes honestly.