I think those who have put some thought into it, and truly want their account deleted, will just PM an admin the correct way and have it done.

Those who post "delete my account" or "goodbye" threads, either:

1) Haven't read the rules and don't know how to go about it the right way (the onus is still on them though to have read the rules though, so this is not an excuse)
2) Are having heat of the moment emotions and somehow believe making a post will make the process faster
3) Are making the post in the hopes that people will reply with reasons for them to stay

I think it would just be so much easier if people read the rules and followed them. "Delete my account" posts are not at all necessary, and affect others in the community.