Why do Swedes not understand Danish?

This one is for my Swedish friends, I'm sure they'll relate.

When I was in Stockholm, I heard a lot about how most Danes understand spoken Swedish perfectly, but Swedes, especially those in Stockholm, often have a really hard time understanding Danish (this is curious mainly because Swedish, Danish, and Norwegian are very similar, and most Scandinavians can read newspapers in all three languages).

Well from "Language in Society" by Suzanne Romaine comes this interesting clue:

"However, Norwegians and Danes claim to understand Swedes better than Swedes claim to understand either Norwegians or Danes. How can this be? Studies of mutual intelligibility are not really about linguistic relationships... but about social relationships, since it is people and not the [languages] who understand or do not understand one another. More Norwegians and Danes have been in Sweden than Swedes have been in the other two countries. Only a quarter of Swedes claim to read anything in the other two languages. While 41 percent of Danes and 52 percent of Norwegians listen to Swedish radio, only 9 percent of Swedes listen to Norwegian or Danish radio... more accomodation is made towards Sweden and Swedish because Sweden is a larger and wealthier country."

This is a good point, that mutual intelligibility is shaped as much by social linkages as by the grammar and pronunciation of the languages in question. Most of the Swedes who've mentioned Danish talk about how the Danes "swallow" letters when they speak, which is the most common reason I've heard for why it's hard to understand Danish. But I bet if people spoke and listened to more Danish in Sweden, a lot more Swedes would start to understand. Thoughts from friends in Sweden?

PS There's a lot of American English on Swedish television, and most Swedes seemed to understand my English just fine (or pretended to), even though I swallow words, chop them in two, talk quickly, and mumble. Interesting....