Why don't they use O(n) algorithms in order to sort arrays?

[Talikag]

The Bucket Sort, Count Sort & Radix Sort are algorithms which only take O(n) operations in order to sort an array. They require additional information, but it's not much of a problem because it's possible to find this information and the algorithms will stay O(n).

Yet, usally when people want to sort arrays, they usally use Quick Sort, Heap Sort or Merge Sort.

However, if the size of the array is big enough, the O(n) algorithms will be faster.

So why do people rarely use these algorithms?