I go into the wilderness to immerse myself into the wilderness. The less of "man" you bring with you, the more you can appreciate the wilderness.
I want to absorb the environment, to breath in the sights, smells, and sounds -- not bring barriers that separate me from the wilderness. For this reason I don't bring phones, MP3 players, books, eReaders, GPS, or even a camera on most trips (camera is only used to share certain trips with my children).
I don't build fires, because they separate me from the wilderness.
I usually don't bring people either, because they separate too with talk of politics, sports, news, war, etc. Solitude allows one to spend all their time in the wilderness unencumbered by man and his man-world. To spend more time, especially at night, to ponder the wilderness world, to look at it, to see it, to smell it, to feel it. Do not confuse solitude with loneliness; there is too much to see, do, and take in; which does not allow for excess time to engage in loneliness. The exception is occasionally sharing the wilderness with my wife or children.
Usually I sleep under the stars to wonder about the grandeur of the universe. In poor weather I use a tarp or similar open shelter, so I can still see the environment around me, winter storms excepted.
And when I return to the man-made world, it allows me to appreciate more, the good of it, and to despise with greater clarity the worse.
So no, I do not bring a phone. It provides no useful purpose. It is a burden. It is extra weight that weighs on soul.