There are many advantages to using custom software. Programmers develop it to meet your needs. Yet, off the shelf software provides different benefits.
Availability is one advantage, with off-the-shelf being easy to buy.
Price is another factor: custom-written software created for you has a specific price. Developers divide the price for off the shelf products between all potential clients.
Updates are another vital aspect. Commercially produced platforms usually offer regular updates, at a low cost. They also check for bugs often. Custom software requires custom updates at a high price.