Martyn,
Heresy probably! 
There is no group policy on this, the individual web editors run their own sites in what they feel is the most appropriate way to suit their circumstances.
This is a relatively small Forum and most of the participating members are actual modelmakers as opposed to those who buy, run and sell their models. We do have a Buy, Sell and Trade facility but I prefer to restrict it to members who contribute to the Forum and share their skills, experience and of course their models.
Unrestricted access to the sales facility just invites people who join to sell their boats and gear and avoid internet auction house sales commission. They have no interest in supporting our forum as such.
Also, many people use the 'Latest Posts' facility to look at active topics when they log on and I don't want that clogged up with items for sale which is what would otherwise happen.
The matter was discussed at some length recently here:
**LINK**
You may not necessarily agree with the policy on this site but hopefully this does at least explain it.
Colin