For networks to work well according to human standards, they are engineered to have spare capacity.

Imagine you wanted to make a phone call and most of the time, your mobile network said:

"Sorry, all channels occupied right now. But if you're willing to pay double the normal call rate, we can kick someone else off"

Yes, this is an analogy about the block size cap discussion on Bitcoin, which is what provides the capacity to transact... smoothly or not.