The problem with the Droid Maxx is that it is based on the unusual processor / chipset used for only a very short time, for the Moto X (2013) and the Droid Maxx. That platform was quickly orphaned as Motorola went to a more standard platform. So maintaining updates for that platform is not a priority.
The Lollipop update was pushed out for the Moto X (2013), which suggests it wouldn't be an appreciably large amount of work to work one up for the Droid Maxx. But the Maxx does have a few hardware differences, such as wireless charging.
Not to mention that the Lollipop update that did get pushed out to the Moto X, even 5.1.1, has its issues. And, honestly, Lollipop isn't that huge an update to Kitkat 4.4.4.
Anyway, Verizon doesn't seem that keen on the update, and Motorola certainly isn't. So there you have it.