One reason the are still in the game might be...
1) The aircraft is under 5,7 Tons which significantly reduces the landing fees on major Airports (depending on the package sold might be neglectable but for a tight budget it can make a difference. There are plenty of Airports where a VLJ pays for example 40 EUR while the next bigger one (CJ3 for example) is in the 350 EUR Zone...)
2) Most operators with Mustangs such as Blink or Globejet depend on broker sales and therefore many sell One-Ways to compete on Avinode and if they are lucky enough to combine two One Ways with another "full fare" deal from A to B the revenue grows... Of course that market is "very low" cost and sometimes risky the more remote the destination is or the less popular the destination is (Nice, Olbia, Ibiza, Palma in Wintertime... Not a guaranteed winner!)
Number 2 of course is just exemplary for all broker focused operators
