They are a pet peeve of mine too. Like you, I feel like Disney is double dipping. The parties really skew crowd levels too. During party season at the MK if you go on a night that does do the fireworks (a non-party) night you get much heavier crowds than you would get for a normal day that time of year.Those hard ticket parties just irk me. Throw out your regular guests early so they can collect double the number of admissions in one day.
Grrr…
I did a Christmas party once (and that was one and done for me) -- It was a sell out and IMHO it was way too crowded. I like normal park days better, but then I am a morning person too.
Sure the MK is always fun, but it's a little bit of a loose / loose to me during party season.