Do you buy a car which best suits the needs of your neighbour? No, exactly. Likewise, software which your company runs on must fit all the requirements of your business. A generalized (mass-market targeted) software can neither give you 100% satisfaction nor can it give you 100% output for your business. If generalized software works satisfactorily, it cannot fulfill all the requirements, which in turn makes you, spend more money.
Benefits of your own software: The software exactly runs as your business does, No special training needs to be given to work on software; just general computer knowledge is enough, Less up-gradation cost, as all your requirements are fulfilled when software is developed, No licensing: Spend once and it's yours. Only you spend is for maintenance and service, which is very nominal compared to software cost.