Why does Ubuntu have Evolution, not Thunderbird?

[prizrak]

With regard to the comments about Gnome above, If I installed Thunderbird do I have to retain Evolution? I don't use the Calendars, Memos and Tasks functions. But does Evo have to be on Ubuntu installations for Gnome to work?

It is actually fairly integrated it is possible to unistall a bunch of it but there is stuff that needs to be kept. For instance the deskbar is dependant on it to some extent. It doesn't take alot of space so I generally opt to just keep it. Although I hate to have duplicate software on my system.

[stig]

Well, evolution would eat few megabytes of HD-space, why not simply leave it there?

I guess I just have an aversion to having the HD cluttered up with unused software!