MySQL not using double-column index
The name of your index suggests, that the index is on (status, created), correct? Then it's exactly what you mentioned.

An index works best, when it's as selective as possible, or in better words:

The closer the result of number of distinct values / total number of rows is to 1, the better is the index. 

When you have very few distinct values, it's often cheaper to just scan the entire table, than to look at the index and then find the corresponding entry in the table. That's most probably the reason, the index isn't used. The fact, that you also filter by date, doesn't help much, because you have created as second column in the index.

The order of the columns in a combined index is very important. Always put the more selective columns first. In your case it might help (very much), if your index would be (created, status) instead (depending on how much rows per day you have and how much rows in total).