I can enumerate why anything in the world is suboptimal. It's not a very strong point on its own.

But notice that you haven't suggested an alternative. You're just lamenting one of the few, generalizable, cheap resources a website operator has to avoid abuse in a world where it's only getting easier and easier for bad actors.

Your analysis is just as thorough as "but somehow it's OK to put locks on every door because some guys are abusing the system o_0?!" Food for thought: Is everyone encumbering their life with keychains for the fun of it? How do the trade-offs look? Do locks play any role beyond feeding the locksmith industry? What other options do people have and how do they compare with buying a $17 lock for their front door and installing it with a few screws?