I think there are a lot of good reasons to go on a party night even if you miss some of the festivities. Technically you can get into the park at 4:00. That's a good 8 hours of park time if you can make it until midnight. And it's $75 as compared to park day when it's $105. Unless you typically spend all 12 hours at the park the 8 hours for $75 may be a better deal. Even if it's not equal 100% in value at least in those 8 hours you can probably get in 2 FPs, enjoy shorter line time, and still have access to characters and some shows.
Sure eating dinner may take a way from some of the specialty Christmas party events but if you don't mind missing some you can still enjoy a lot from 4:00 - 12:00 while still doing a TS meal.
Now if you want to get in every character meet and greet and every
MVMCP event then dinner doesn't make sense. But for people who want a mix of just being in the park for 8 hours at $75 and who want the rides and then to experience some of the special events then I think it makes a lot of sense.
Also, other than Wishes, most shows occur multiple times throughout the night so I would imagine even with a dinner you'd get to see most shows.