I feel like cantrips should only cause surfaces if the player targets the ground with them. That way there's an opportunity cost to using Ray of Frost to freeze a pool of blood and cause enemies to slip up.
Similarly Fire Bolt can be made a 1D8 again and still be able to be used to set oil and stuff on fire, but you don't randomly get an extra 1-2 damage because you set the floor under the person who got hit on fire too.
I really like the utility that surfaces offer. It feels very DnD to be able to cover the floor in grease before setting it on fire to burn a bunch of enemies, even if that isn't how those spells work in the rules as written. But getting the surface effect as a side effect of doing damage is a bit much. Making it a choice would go a long way to encouraging more tactical thought in how they are used.
+1
