I don't think it is belief in these "beings" that is the main point of the teaching - that we can remain agnostic about. Rather it is an understanding of the moral cause-and-effect between past, present and future states, which would include rewarding or "heavenly" states, and deprived or "hellish" states, that is vital and would be a hindrance if rejected.
"And how is right view the forerunner? One discerns wrong view as wrong view, and right view as right view. This is one's right view. And what is wrong view? 'There is nothing given, nothing offered, nothing sacrificed. There is no fruit or result of good or bad actions. There is no this world, no next world, no mother, no father, no spontaneously reborn beings; no brahmans or contemplatives who, faring rightly & practicing rightly, proclaim this world & the next after having directly known & realized it for themselves.' This is wrong view..."http://www.accesstoinsight.org/ptf/dham ... index.html
That said, I do believe, because I don't really see any difference between aforementioned states and the beings inhabiting them.
"If beings knew, as I know, the results of giving & sharing, they would not eat without having given, nor would the stain of miserliness overcome their minds. Even if it were their last bite, their last mouthful, they would not eat without having shared."