By "weird" here I actually meant those deemed socially or economically harmful or untenable, such as slavery, mandatory periodic absolution of debts or polygamy

By "weird" here I actually meant those deemed socially or economically harmful or untenable, such as slavery, mandatory periodic absolution of debts or polygamy - laws that are just weird but without direct adverse impact are being deliberately kept on as means of reenforcing in-group cohesion through ritual - aka "tradition".