Or there WAS a good reason at some point anyway. Often a traditional serves a social or practical need- but That tradition may become outdated by changes in the times etc. A previous generation may carry a tradition over to a younger, and then it morphs and changes with the times. Wedding rings in the West have a long history that has gone through many changes for example.
A superstition which said taking a pie e of a brides clothing led guests to often tear a brides dress to shreds. So brides began throwing clothing like the garter to stop this. Later, grooms would remove the garter themselves and throw it to the male guests to prevent drunk and ornery men from removing it themselves. It followed that the women would want something as well and this the bouquet toss cake about. There is an example of a “fun” tradition which in modern society lost its original need (hopefully anyway...) but still ensures- the same idea of “luck” has transformed to “whoever catches this will be married next...”
Other traditions come from economic need etc- many familial and clan type traditions come from these types of needs. In a harsh environment with little or no social services, family or neighbors would care for each other, knowing that if they were in need they would require the help of the others too. It was often the only practical way to survive and had benefits over those not acting as a group.
It's not just that
There's usually a good reason that the tradition exists in the first place