This was done because people would ask a question in the homework section, get their help, then delete their posts and leave, never to returen. It is assumed this was to confound their classmates and professors.
There is a formula that increases the number of posts required for senior member status based on your font size wth respect to 12 points. It's (x-12)^x where x = font size. For fonts less that 10, it's (12-x)^x.
Also embedded is the troll recommendation trigger, for fonts greater than 36 points. It shows up on Senior Members screens to remind them to ignore the trolls.