I think that new consumers like PDF's because they know them and know that Adobe can read them and its been around for a while.
The other file types that ebooks come in are strange and not always standard, so PDF's make sense to a new consumer.
When I first started buying ebooks I would buy them in pdf format. Now I try to not get ebooks in PDF format.
How often is PDF support asked for in the "Which Device Should I Get" forum? Very frequently.