Well from what I understand of Traveller fuel requirements, yes energy is abundant, but cheap in regards to time and vulnerability is not accurate. Ships that use such engines routinely are fueling up at gas giants, and gas giants are a fighting/conflict point between powers in Traveller because they are the vital oil fields of space.
So a high-energy setting is still vulnerable to fuel shutoffs and exploitation abuses by those who control gas giants because the market does not control the production, in many cases the setting is more Feudalistic rather than Capitalistic. From reading and talking with various folks on the basis of Traveller-lore, an assumption that cheap makes scarcity non-existent is inaccurate. The fuel is cheap because it's unlimited in quantity, but not in location. Those who have access to it have unlimited travelling potential per se, but we aren't in a friendly "I share my gas giant" kind of setting, are we?
Therefore scarcity still exists, just not in the form that resources will deplete over time.