The financial services market is a good example of where custom software often still makes sense. For example, a bank may develop its own balance sheet rating application, hoping to better judge the risks involved in business loans, and thereby reduce the losses caused by loans that are not paid back. To the right side, the features desired only by one customer are located. Custom software works best for products targeting the right side of the spectrum, since there the market is too small for standard software. There also exists more specialized standard software for particular types of businesses, e.g., packages for dentists, accounting software, and so on.
Standard software is inexpensive, at least compared to the cost of custom software development.
Buying standard software can be done quickly, in particular if you already know which product to buy. Someone may have recommended an application to you, or you may have read reviews and comparisons in journals. This limits the risk you take. Once you have bought the software, you need to install it. Some high-end commercial packages go to extremes in this respect.