Because if they don't other people will hear they don't pay and won't sell them 0days

How long do you figure a criminal reputation typically needs/wants to last? I have always been skeptical of “black market credit ratings”. If you happen to build one up, it’s likely only in order to rip someone off at a higher price and cash in the value of it. It’s not like you’ll need that good rep for your retirement.

	▲	applfanboysbgon a day ago \| parent [-]
		ShinyHunters has been "in business" since 2019 and it is their reputation that resulted in eg. Canvas paying their ransom this year. Without that reputation, it is unlikely a large-scale ransom would have been paid, because the reputation is what gives them credibility that paying the ransom will actually result in the promise being upheld.