My intuition would’ve told me that since flintlock muskets replaced matchlocks, they must be technologically superior. Field cannons that use linstocks are essentially large matchlocks, but many naval cannon use flintlocks; why is that?
Not quite matchlocks: a linstock is a piece of lit slow match held at the end of a stick. Unlike a matchlock, it takes some time to descend, as instead of a short lever moved by a spring it's a rather long lever moved by a human arm. A flintlock is also faster than a linctock. This is key to understanding why field pieces could keep using linstocks and naval gunners would find a flintlock useful: the naval gun is on a boat that usually is rolling. Firing that gun has to be timed, ideally, to the peak of the roll where the boat has stopped moving for a moment. If the elevation changes between shots, the range of the shots will also change. For a broadside at a ship only ten yards off, that's not perhaps very important. But if the ship is trying for a target several hundred yards away, a few degrees of variation in the elevation will matter a great deal. There was also a bit more safety to a flintlock- it was triggered with a lanyard, that allowed the gunner to keep out of the way of the recoiling gun better than with the linstock. Linstocks were, however, retained as backup ignition in case the flintlock didn't fire the gun.
A gun lock (cannon firing flintlock mechanism) had the benefit of the gun captain being able to aim down the cannon from behind and pull the lanyard to fire rather than standing to one side to ignite using a linstock. This was great for naval warfare as it allowed more accurate and swifter aiming and firing of the ships guns. However, ships cannons had a major difference to field artillery - primarily field artillery had less need for swift aiming (stable firing platform), and wasn't heavily limited in its recoil by the ropes and pulleys which tied down a ships gun. The gun captain on a vessel could stand at the "safe" distance behind the gun knowing the recoil would be halted short of the length of the lanyard. Basically you could take longer to aim field artillery, and you definitely did NOT want to be behind it when it fired.
The benefit of a linstock for field guns remained in place because the simplicity of maintainance, the method of firing, the difference in platform and aiming time, and the age or origins of the gun, rendered them often more suitable for army usage.
Furthermore gun locks could not be retrofitted into older cannon, so older artillery would use the means of ignition they were founded with until melted down.