I didn't say that small traders don't exist. I said that small freighters are not going to be what is used for the vast majority of trade, because they are inefficient and less profitable than larger ships.
This gets back to the fact that piracy requires the reliable presence of trade. The reliable trade is going to be on larger ships. Those Type A ships will be around, but they don't follow a schedule, they aren't guaranteed to have full cargo bays, and don't necessarily follow the big trade routes.
The idea of dedicated pirates trying to make a living solely off that does not make sense.
Off the mains the smaller ships were supposed to be the more common ones. Its like trains, they don't go to every town. They go to major ones and people get buses or taxis or use their own vehicles to their final destination.
If you produce 400 Tons every quarter it doesn't come in one 400 ton lump. More likely a few 10's of tons per week. That is plenty to keep a 200 Ton ship busy every week, but of no interest to a ship that can take 400 tons as that amount will never accumulate if the littles cart it off regularly.
It depends what you mean by the vast majority of trade. A 1000 Ton capacity freighter will move 1000 tons per jump. 10 Free Traders might move 800 Tons. The majority of trade goods are being moved by the freighter, but the majority of trade journeys are being carried out by the free traders as they are conducting 10 trade missions to the freighters one.
I didn't say that this was the only source of income for a pirate.
How many ships do I actually have to loot?
I only need KCr5 a month to live like a Baron. Lets say KCr100 for the whole crew. Maintenance and repairs and replenishment KCr50. Mortgage KCr250 per month because I have souped up subbie. Total monthly expenses KCr400. Plus a small amount for rescue bubbles for spaced crews (because I am the gentleman pirate). Say MCr5 per year.
That is a lot of Common Consumables I have to sell, but non-one is shipping them at Cr500 per ton. A more credible average base value for cargo is KCr10 per ton. I need to steal 500 tons per year to cover that. That is 1 ship a month assuming around 40-50 tons per ship.
But:
Am I actually paying a mortgage? - Pirate! That would reduce my expenses by at least half.
Do I need that large a crew. I could use robots instead and save a fortune in the longer term.
KCR10 is a sensible price for common goods, but I could make MCR1 per Dton for Radioactives. If I select my target intelligently I might bring the average price of seized goods to KCr20 without too much effort.
If I have a good broker (one of them fancy robots) and I am not necessarily in a hurry to sell the cargo I might make 10-20% on top.
If the target is uncooperative then I'll loot the Ships lockers and Staterooms as well to supplement my income.
Sometimes I might get a small ship and make my yearly quota in one go.
I don't have to be a pirate full time, I can carry on legitimate trade as well. It gives me a good cover and might pays the bills on its own.
If I am careful I might even get a normal freight job and just keep the cargo instead. It is more risky and I'll need to sell the ship and burn my identity and move out of the area afterwards, but it's easy money.
I might just go raiding and robbing on occasion (or get legit mercenary work - and do robbing and raiding on the side)
I might occasionally demand tribute from small undefended systems and bases. Not too often or predictably and after a careful recce.
Some pirates might sell their captives into slavery or ransom them. I don't because I am the Gentleman Pirate, but all those droids are coming with me to add to my robo-pirate crew. Quick memory wipe and were off to the races.
I don't think it is implausible and frankly MCr5 per year is a fantastic amount of money, but once you have some seed capital you can make it easily through trade. If you don't need the seed capital because you stole the cargo, it is all profit and you kick start your trader career.