Nobody is going to give away "free" money. From whom are you going to borrow the stock in order to short it?
When a stock goes under $5 it becomes difficult to short. Few companies (big caps) are still sometimes shortable... C is a good example. Most companies facing the possibilities of bankruptcy/restructuring are not shortable. Shorting a stock that is in this stage is also very risky. What if it is trading at $1 and someone is willing to buy the company for $2. You could lose some money on any good news.