I imagin it's a bit of a love/hate relationship LEGO has with investors. As you mention, revenue is generated, but I am sure they hate a couple things - A: Product Shortages of hot selling products, because that upsets and drives away "normal" consumers, and inflated prices of current prices when out of stock as customers aren't always smart enough to differentiate between a reseller and a LEGO outlet. They just know they had to pay XXX dollars for a set above MSRP and they are pissed off. LEGO have a reputation of being too expensive as is.
Similarly, I would say increasing resellers probably make it trickier for their R&D and Marketing department. Numbers aren't always accurate regarding supply and demand, since they have a hard time knowing what's being bought by customers as opposed to resellers in what volumes. Product cycles are planned years in advance, and skewed numbers can gum up the works.
So, all things considered I would say LEGO more or less tolerates some/most resellers (Again, I am sure the vast majority of us could be banned pretty easily from ShopLego if someone cared enough)
But again, for those complaining, remember those same policies are basically what allows aftermarket prices to stay high. So we can't really complain. And I aware of very few, if any people - who were marked by LEGO as resellers and banned who weren't actually reselling. So...