When you spend all day in a swimsuit and the restaurants around there have a dress code you dress for dinner. Dressing for dinner is kind of a fun throwback to a different era and the ritual is a fun part of the day. I also have fond memories of my parents coming home as a tiny child and my nanny changing me out of my play clothes into something nice for them, who we hadn't seen for awhile.
I'm someone who likes to get dressed in the morning - wearing, matching, and picking out clothes is something that is pleasurable to me. Even when it's a snow day like today and I'm in jeans, a black fitted T shirt and a fair isle sweater I didn't just put clothes on - I got dressed and I enjoyed the (quick) thought process that went into dressing for a cozy day at home with JR.
Dressing for dinner is just an extension of that - it breaks up the day, allows you to come to dinner ready for dinner. In Mexico, it was mandatory. At home it's optional but sometimes I do it just because. I put away the work clothes I've been in, run a brush through my hair, and wear something nice to dinner. I don't require it from JR but he often plays along, changes his shirt and washes up too and it really sets the tone for good conversation and lingering, which isn't done nearly enough in these days of 20 minute meals and eating on the run.