It does, but a network protected by 1 TH/s can be attacked by a guy spending $100 bucks on a S9 and just unplugging his AC for an hour and he has enough to reorganize 20 blocks, the other takes about ...2 million $10k machines to do, and about 10 nuclear reactors (depending on size)
One is Bitcoin, the other is Bitcoin gold, which got successfully attacked via a 51% three times.
Which one do you prefer?
Of course, the value I indicated was merely indicative, to mention that everything happens the same way with a lot or a little hash.
Regarding the famous possible 51% attack, unfortunately I see it more likely to happen as mining becomes centralized in half a dozen large miners and pools, than the other way around.
Since we are talking about the future, in 20 years, there will probably only be 2 or 3 pools left, which will together concentrate +50% of the hash power. What prevented them from getting together and organizing an "attack" on the network? Anything... The world is full of examples of lobbies, when 2 or 3 large companies in a market come together to align strategies.