I dont. And to answer the question of why its the summer solstace? Solstice means Stationary. Today happens to be the day that day and night are equal. Please remember that when this tradition started, they werent in america =)
In the northern hemisphere, the longest day of the year (near June 22) when the Sun is farthest north. In the southern hemisphere, winter and summer solstices are exchanged. The summer solstice marks the first day of the season of summer. The declination of the Sun on the (northern) summer solstice is known as the tropic of cancer (23° 27').
The summer solstice is the longest day of the year, respectively, in the sense that the length of time elapsed between sunrise and sunset on this day is a maximum for the year. Of course, daylight saving time means that the first Sunday in April has 23 hours and the last Sunday in October has 25 hours, but these human meddlings with the calendar and do not correspond to the actual number of daylight hours. In Chicago, there are 15:02 hours of daylight on the summer solstice of June 21, 1999.
The summer solstice long ago was incorporated into the Christian calendar as the feast day of St. John the Baptist. Just as John was the forerunner to Jesus, midsummer forecasts the eventual arrival of the seasonal turn of mid winter. Hundreds of years ago throughout Europe, most healers were women who used herbs. In the twelfth century, Hildegard of Bingen wrote a book of natural healing and herbal methods. It became the basis of modern western herbalism and medicine. Not long after publication, the Inquisition began and nine million women were executed for witchcraft. Witchcraft could be defined as "The knowledge and practice or the traditional ways of healing."
The summer solstice is the time of year when the feminine earth energies are at their height, this day being the optimum for gathering herbs and for healing. Some of the herbs gathered on the solstice where mugwort (the herb of St. John), chamomile, geranium, thyme, and pennyroyal. These herbs exuded a wonderful aroma when thrown on bonfires during midsummer festivals. Summer solstice bonfires were burnt throughout Europe. It was supposed to banish sickness from livestock and bad luck.
Does that explain it?