"I personally like to dress up, and I couldnt care less what other people do."
I thought I shared that sentiment, until my last cruise (not HAL). One of my tablemates waited until the maitre d' was distracted, and slipped into the DR wearing cargo shorts, safari hat, sandals, and t-shirt. Everyone else at our table and surrounding tables was in formal attire.
For me personally, it took away from the atmosphere and ambience of formal night.