I don't know how you've gotten things so backwards. Of course we want new members. We also want them to find the forums useful. Allowing them to post from the start is a huge part of that. Can you imagine having a question (potentially a pressing one), going through the effort of signing up to a community, and then finding out you couldn't do anything? I certainly wouldn't be back.You've basically proved my point, views matters. As I also pointed out, advertisers are not interested in existing registered users seeing their ad's they want new registered users because a new registered user means a new view and every new view on an ad means more money to MR and this is why MR will not change it's policy on how it handles newly registered users because the site owners knows it could affect them financially.
The vast majority of spam never makes it into the forums. We do occasionally have attacks that manage to evade our defenses and are able to cause issues until we can counter them. That's a trade-off but it's one we're making from a user standpoint, not a financial one.