Xliest I already addressed that multiple times, but yet again - it's because we don't need to rely on archaic and unreliable and annoying methods of trading when we have the tech and capability to make a better system that eases the burden for all users and ensures all parties get what they're looking for and increases the time to make a deal from days/weeks to seconds. It increases accessibility to buyers and broadens the market for sellers, thus improving prices for everyone and improving the user experience.
Theres zero downside to having a marketplace, not for goods and not for magic.
Do you think after 30 years that if Thardferr had continued being developed that it would not have had a player driven market by now? That preposterous.
Anyway I don't want to post an ad looking for a caster, and then haggling for a price, and then hoping they will deliver, and hoping they can cast at the times I need, and on and on and on. That's just dumb. We can obviously make a much better way, and we are going to.