Excellent follow up question!!
There's a difference between reading through code, and READING (actually loading the program into your mind as your reading). I do that because it let's me know, where ever I am in code - that the variable holds a jQuery object - so I already have the jQuery goodness w/ it. I can't take credit, and assume this is a common practice that I read from someone much smarter a long time ago.
So, by your naming of myUserFormItems --- if I see that later in code - I don't know if it's an array of strings/ints/floats/objects, concatenated string, or some other object - I would have to go find where it's assigned and "load this script" into my memory - which has limited capacity as it is.
While you just wrote the code - you inherently know right now, but a couple weeks/months down the road, if you must revisit, you have to read and focus so much more to understand the code. Where little cheats like pre-pending the jQuery object variables with $ - it eases the understanding and readability of the code.
In a very short/small function such as what you showed it's a moot point, but in larger functions/objects, it becomes much more valuable. And consistency is key.