If I could play devil's advocate for a moment
Don't you think that going from station to station every 5-10 minutes is going to get a little... stale?
Using the figures of 600 per ton and say 7 mins per trip on average. A type 6 with fuel scoop etc has a capacity of 96t. So 96*600 = c57,600 , so that * 8.6 (60 mins/7) gives us c493.714 per hour.
Now compare this to rare trading with the same ship, in my experience it took 110 ish mins to fill up plus 45 mins to fly back for a profit of c1,440,000 which is about c557,419 per hour.
We can see that the actual earnings were pretty close to station tramping(given the credits needed to actually do the runs anyway).
The question is simple. Why direct those who want to trade into a demented honey bee pattern, when the wider ranging but taking a longer/more perilous route was to many more enjoyable?