Sales will drop, but even so, Valve will never admit mistakes. You can see that clearly when they have been proven wrong multiple times, but they stick to their "solution" nonetheless.
I just thought about this. The new system doesn't even affect chargeback scammers.
1) Open a throwaway Steam account in the most expensive region.
2) Steal a credit card, buy Steam wallet credit (or Paypal/Paysafe/whatever credit to buy wallet credit).
3) Offer AAA games on the grey market at a much lower price. (The card is stolen, so they won't care if they "pay" 100% of the price.)
4) Sell stolen goods, profit. The money is laundered.
5) Customer gets game as a gift, can activate and play it for the time being.
6) Credit card owner charges back the stolen amount.
7) Steam revokes and invalidates the license*.
8) Grey market customer gets their money back (and hopefully learns from their mistake).
Nothing has changed for chargeback scammers.
Nothing has changed for the scammed.
Nothing has changed for the grey market sites.
Nothing has changed for Valve. (Except sales drops.)
The change ONLY affects legitimate users.
* Step 7) shows that the argument that Valve paid the fraud bills is not true. Licenses from credit card fraud are revoked, no matter if it's keys or gifts. Humble can also revoke key licenses if they don't get their money.
The solution is simple. Bring back the old gift system, but only allow the purchase of gifts to users that already have a significant library of their own. That way, throwaway accounts can't purchase gifts. And no scammer uses real Steam accounts.