"Why is it on the left hand? I mean, I am sure there is some reason from back in the day, but it's just not practical."
there are quite a few different reasons from various bits of lore. the three most common parts are this:
left hand/third finger:
in very ancient tradition, it was believed that there were major veins that ran directly from the left third finger to the heart. with the heart's association with love, it was an easy step to wearing the ring as close to the heart as possible.
third finger:
in medieval times, in christian ceremonies, the groom would set the ring on the first finger, then the second, then the third. this was a representation of father, son and holy spirit.
left hand:
in many varied traditions, only one ring was worn, as opposed to today's seperate engagement rings and wedding bands. one ring was given to the woman. before the wedding, she wore it on her right ring finger. during the ceremony, however, her betrothed moved the band from her right hand to her left.