I work in Seattle, and can tell you that there are a lot of software developers who do not train in any martial art. And you know what? They do just fine, for the most part... never miss those martial skills that they don't have. Should they ever need them, though, they might wish they had trained and competed in MMA (or some other competitive style). And I can tell you that the converse is true, as well. Those software developers who do train in MMA, BJJ, boxing, etc, are much better prepared than those who do not.
Experience is cumulative, and it's about logging hours doing things. In the same way as above, a bouncer that competes will benefit from the competition. Or said another way, a bouncer, who also trains and competes in MMA will have a more well rounded and reliable skillset than one who doesn't. A bouncer that competes will benefit from the competition.