There's even more to it
Problem #1 : Nokia doesn't support their phones
This is a huge problem because when you buy a Samsung Galaxy or an iPhone 4S, you know that this phone will be the true love of the company who made it for months if not years after it's made. With Nokia, you can't even be sure anyone outside of marketing can remember it.
Problem #2 : Nokia doesn't support their phones
Everyone in Europe can tell you about how their first mobile phone was a Nokia 6000 something. It was simple and worked awesome. This was long before software updates or mobile Internet. But they don't have Nokia anymore because everything that came after felt like junk that was hacked together quickly.
Problem #3 : Nokia doesn't support their phones
At any given time, you can find dozens if not scores of latest and greatest Nokia models of phones. Even for a company the size of Nokia, there is no way in hell that many phones can actually be supported. And for every one phone you see, there are two that are being developed of which only one will ship. When you buy Nokia, you're buying a device and that's it. Buy a Galaxy or a iPhone and you're buying a device to access a full user experience and service.
Hell, Nokia's been shipping Windows Phone for weeks and already they have more models out of Windows phones than Apple ever shipped of iPhone.
Problem #4 : Nokia doesn't support their phones.
Updates to the operating system will be targeted at a few specific models. There's no guarantee that you'll get an update to your phone later on with a phone where the manufacturer just doesn't care what you do with the phone after you buy it.
If you don't believe me about these 4 major problems, watch Elop's presentation of Windows Phone and see how much he actually focuses on anything other than what it ships with.