While you and I may be perfectly capable of maintaining transaxle fluid, not everyone else is. And if the way to ensure that fluid doesn't get contaminated or the wrong fluid gets used during the warranty period (and remember, that was the prime reason for A604/Ultradrive/4*TE failure in the past - the use of incorrect fluid) is to seal the system and make it a dealer item, then that's what happens.
Chrysler is not the only automaker that does this today.
And, as IC notes, there is a procedure available should you want to tackle it yourself and take on that responsibility.