In my opinion, there was no "real explanation" as to why Symbian phones can and Maemo phone can't. Put yourself in the shoes of Joe the End User. Here is his friend with a Nokia phone that can do free turn by turn navigation but poor Joe can't because he got the last Nokia phone with Maemo. Just imagine what is going on in his head : . Nokia's fault or Joe's fault I can't tell.

PS: By "real explanation" I meant something that end users will be able to digest. Remember that "but it is a different OS" might not be a good explanation for somebody whose definition of a different OS is Windows XP vs Windows 7.