Most ordinary citizens doesn't really care about their electronic devices especially cheap item like the computer mouse. So when it is faulty then just throw them away since it is very cheap and convenient to get as it is available almost every electronic stores. But if you are very detail you could salvage some of the parts for re-use.
The USB cable can be re-use for project purposes at many computers and devices today have USB port connection. Secondly the left and right switch button can be re-use to replace other faulty mouse. Commonly the left press button is always get faulty first and it is the most used every - single day someone use the computer. However the right button is rarely use and that can replace other mouse press button which are faulty.
For example I've logitech wireless mouse which is quite expensive to buy a new one - and the left press button is worn out cannot be press properly. But then I've a faulty cheap mouse to take the right button to replace the Logitech left switch press button. It works perfectly.
The roller wheel switch also can be useful for enthusiast electronic project as well as the press switch button of the roller wheel. The central mouse IC can be used to make transceiver trigger mechanism to transmit button click signal. There are a lot of ideas on this one which you can think off.