So my first thought is to ask that the initial title and question posed in this thread be changed. It presumes that God creates disabled people, which from the sounds of the responses not many people agree with.
I don't believe God does so. As has been stated in previous posts, I believe He created this world for His wise plan for us, but for the most part lets it proceed according to natural circumstances. Is it fair? Absolutely not! Which leads me to believe He did not intend life to be fair, at least not certainly as we mortals view fairness. Otherwise we could similarly ask why did He cause some of His children to be born in affluent families and others in third world poverty, or into slavery, or where they will never hear His word, etc.
I believe He allows what trials happen to different people to just happen, just as He allows some to be born with greater advantage in life. We all have different journeys and different afflictions and challenges. But He doesn't ask us to have the best hand at the table, just to do the best we can with what we've been dealt. Per the parable, some are given more talents than others, and the judgment doesn't come to who ends up with the most, but to how we handle what we've been given.
In saying this, please don't feel that I'm suggesting an attitude of just deal with it. Indeed, we should all be moved with empathy charity to those who have such challenges such as a disability and do what we can for those people. Whatever else you may believe about Him, we would do well to all follow Jesus' example, which included showing the most tender compassion to those in such a plight. Indeed, though Him we have hope through all our dark times and challenges.