In medieval Europe, a bride typically did not expect to wear her wedding dress again, and the dress was considered good luck for other women, a type of fertility charm. After the wedding, single women chased the bride and ripped pieces off her dress, leaving her in tatters. Over the years, wedding dresses became more expensive and it became traditional for women to keep them, either as a memento or to pass on to a daughter for her wedding day.
To prevent guests from ripping the wedding dress, brides began throwing other objects as a distraction, one of which was the garter (an elastic band, usually decorated, worn around the thigh just above the knee to used to hold up stockings). Later, the bouquet became the most traditionally thrown object. The wedding bouquet is particularly suited to this use, as flowers symbolize fertility, and as perishable items, they are not something the bride would wish to keep. The bouquet is also a safer item to toss than the garter, as unruly and impatient wedding guests were sometimes known to try to take the garter from the bride while she was still wearing it. Lol.
Bottom line, throwing of the bridal bouquet seems to me like a tradition that isn't going anywhere anytime soon. It excites guests to see who the lucky gal to catch the bouquet is and just generally adds to the fun of the ceremony. By the way, I caught my best friend's bridal bouquet and I was the next one to get married. Imagine that! True story.