Should you play all 5 roles?

Now that the improved queuing has been introduced where you are only required to main two roles, is there a point to playing all 5 roles besides filling? For example, learning enemy champion kits and cooldowns, or learning other mechanic that are more important like wave control for a top laner to be used as an adc for bot lane. Do you think it is useful to main more than 2 roles?
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