some specific field yahoo is the best and most popular.these are ymail and yahoo messenger.yahoo answer is also good platform for increasing knowledge through different information.
I don't know why people like it , but I like it for -yahoo answer -yahoo messenger -news -mail service. that's it.
People who started with Yahoo remember this to be a good service. That might be the reason this is more popular with the people who are more then thirty year old.
It provides too fast service than others media. More over yahoo answer is the best teacher of many person.