In the 1980s this phrase was used widely to justify buying from an incumbent supplier of pretty much anything. It suggested that by sticking with a proven brand, the individual could mitigate the risk of getting a decision wrong; that sticking with the status quo was a good idea.
For IBM as a brand this was gold dust - as the referenced article points out, IBM never made the claim but they did manage to position their brand in such a way that their customers would use this phrase as a truism.
For today's Business-to-Business brand builders, there's an interesting point here. Fear of loss is much more powerful than desire to gain and if that fear can be harnessed, a premium can be charged for both products and services.
Now, you can see why the phrase ‘No one ever got fired for buying IBM’ is so powerful. [By the way, this phrase wasn’t said by IBM employees; it was said by their customers.] What does this mean to your sales messaging? If you want to get customers to make a decision to buy your product, you can’t just make a rational argument, and you can’t just talk about the benefits of your solution. Instead, you have to help your customer see the pain associated with doing nothing.