Not stupid in the least the reason was signature spamming to offensive sites, etc. and those responsible for administering the site had to take action.
These same cretins were also spamming the PM system which is also part of the restriction. People were receiving offensive p-o-r-n-o-g-r-a-p-h-y so the decision wasn't one taken lightly. Unfortunately their actions have an impact on legitimate forum members.
For a period of time no one could use the PM function but the bar was lowered to restrict only new members.