They may save on average, but that's just shifting the expense to the customer in terms of wasted time. If there is anything I've learned over 30 years of running businesses that being disrespectful towards your customers' time it is that you will end up losing those customers.

Another way they save is by discouraging their use. Since people who've called with real issues have had to waste a whole lot of their time, they're more reluctant to do so the next time they have a problem.