In reply to Ciprian Popescu.

A lot of plugins are better than Akismet. Akismet is not a free plugin for most purposes and Automattic benefits from it, so including it in the core is more or less unethical. Akismet sends information to Automattic servers for one, and a lot of other solutions work great (or better) without sending your data to third-party servers.

WordPress Core should not have any plugins in it, and it needs one default theme.