That Ask.com still has 1%-2% of US search traffic is astounding. It must be people using browsers with the default search engine set as Ask and not knowing any better.
It sounds like his dad never tried Google, thus there was nothing to "stick".
I think the lesson here is that while the search engine switching cost is $0, people are creatures of habit and may continue using something long past its expiration date if it is returning expected results.
What we see from this case is also why IE has such a huge market share. Less computer literate people will start using whatever some more experienced entity tells them to, and will keep using it until/unless they are forcibly switched to a new platform.
"The search business grew 20 percent, goosed primarily by a 55 percent increase in active toolbars to 97 million. IAC’s toolbar business is its secret distribution weapon"
http://techcrunch.com/2010/10/27/iac-third-quarter-25-percen...
They get a ton of distribution from software installers that ask if you want to install other stuff during the installation process.
Unfortunately I can't point to anything I searched for recently to back this assertion up.