What kind of half-assed robot can't use contractions anyway?
They're in the dictionary, they're real words.
He either doesn't like to use them, or likes to lie about not being able to.
Actually some real people with autistic-spectrum conditions like Asperger's Syndrome prefer to use formal language. For instance:
Aspie kids talk like very short adults- Due to a very concrete understanding of language and advanced verbal skills, Aspie kids select and use their words carefully. Their vocal affect may sound stilted, or as if they are reading a speech off of note cards. They avoid lazy communicating, such as using slang or contractions. Instead of saying “I’m gonna’ go to karate after school, yay!” they would say something like “When school is finished I have a karate class. I like karate very much, and I am excellent at it. There are 7 kids in my karate class. There is David, and there is Robert, and…..” Aspie kids also usually don’t know how to end sentences or switch topics, and will often keep talking about a particular topic even though the listener is showing absolutely no signs of listening.
Essentially Data's behavior in a lot of respects is very much like that of a person with Asperger's or high-function autism.