I use profile pages extensively. Profiles are critical for the functioning of my wikis, as I use them as part of my teaching. Without profiles, it just become too burdersome to see who has done what. With profile, I only need to click on Recent contributions and Recent posts by a particular member/student to have that info.
Furthermore, profiles offer the reader the opportunity to see who (i.e. how serious) a member is. Any contribution by someone with a "weird" username, without profile identity and with few contributions will probably be deemed less serious than any contribution by someone who uses his name as username, has a profile indentity and several contributions of quality. One thing where Wikidot is better than other wikis (for example, Wikipedia) is that users' contribution can be traced because they have a profile. Otherwise, pages become no more than a place were anonymous users dump information.
On the other hand, if the profile page is deleted…wouldn't the spammers use front pages/start pages for the same purpose? And if these are, therefore, blocked, wouldn't they use secondary pages, then? Deleting profile pages may, thus, not solve the problem, while, at the same time, limits Wikidot's functionality in the long run.