• ritual casting doesn’t consume spell slots
• some of the catoptromancer’s features already look like rituals, it would be logically inconsistent if catoptromancer was allowed to have rituals but therest of the class wasnt
• the spells known is already a very good limiter
• adds utility to a class that could struggle with that potentially, due to lack of spell slots which would most likely be spared for combat or very important moments

ritual casting should be allowed as long as the player has copied the spell