Here's another side of it: kids who can't write cursive can't read it either. Ask a student who has never learned cursive to read a handwritten paragraph. You'll see what I mean.
When my older son (who writes in cursive) did spelling tests at his new school in 4th grade, and they exchanged papers to grade them, not one person in the class could read his words (and his cursive is quite good).
Another problem, along with lack of practice, is the fact that some schools allow keyboarding papers as early as 4th grade. Thats what happened to my son. They gave him a choice so he chose the computer.
I finally realized in middle school that he couldn't write a legible paragraph. He was dependent on the computer and spellcheck. I had to spend a year forcing him to handwrite summaries for me and he complained mightily because his hand hurt after a sentence or two. It took a few weeks for him to relax with the pen or pencil and pop off a paragraph. This is ridiculous for kids about to go into high school English followed by the ACTs.
I also had to re-teach him certain letters in upper and lower case. No teacher corrected his mess when he was doing extended response in class, something they do a lot to prepare for state tests.
Oh yeah, and rarely did he come home with lined paper. He had idea how to use it.
Most of the practice that he did receive in grade school was in the form of journaling. His own thoughts of "I love to play with my ball" are more critical at that time than learning to shape letters properly, apparently.
Cursive is important because they can't read it, like Vicki said. They can't read their parent's love letters or the Declaration of Independence. Cursive gives them more practice which helps to strengthen those small muscles in the hand. At some point, I agree that allowing them to choose is fine, but I would push it to high school. They have to be forced to write until it's fluid, something we of another age took for granted.
I could go on and on, but you get the point. It's another thing you must do at home and early or you'll have to remediate later.
I know a lot of kids who write a '4' the same way they would print a lowercase 'u', except with a longer tail. A '5' is written the same way as an 's', and a '9' is written starting from the bottom, then up, and a counterclockwise circle at the top.
I think they "discovered" this because no one showed them how to pick up the pencil to finish the 4, or to put the "little flag" on top of the 5, or to change direction when writing the 9.
And they hold their pencils the way little crabs would hold them! By the time they get to middle school it would need Total War to fix, and I would lose.