I see two separate debates here. One, is wholesaling legal without a license and two, what value does a wholesaler add?
For debate one, I am a wholesaler and if the law says you have to be licensed, just get the license. There are lots of dumb laws we have to follow every day and this is just one more. Personally I don't see how a license makes someone a better wholesaler. And licensed or no, you are still advertising a house you don't own without representing the homeowner. True, licensees have to be background checked, etc. But as many have pointed out, in all licensed professions, you still find shady people, cheating others both legally and illegally, license notwithstanding.
As for debate two, if you want to know why sellers sell to wholesalers instead of on the MLS, ask some sellers. They all know they could list with an agent. That's how most of them bought their house. I am sure they get agent postcards talking about how much the house down the street sold for. I know I do. Fact is lots of people call the agent first and don't like what they hear, so then they call us.
One time I had a house under contract when the seller said his friends told him he should not sell to me because all investors are crooks. I said ok, if you want to cancel the contract, put it in writing and I will cancel the contract. My end buyer wanted to go to court but I said no; We can always buy someone else's house but a homeowner has to do what he feels is best with his one major asset. Turns out, the guy just wanted more money. Plus his mom was a hoarder, and none of his friends who advised him not to sell to me would come help him clean out the house to get it ready for sale.