Now with 1.14 and all the different versions of AIR, like CAVE_AIR and VOID_AIR, its really tedious to check to account for all those types of air, if you just wanna check the absence of a block.

Adding a method for this would increase useability and backward compatability for the future if mojang decides that we need some more air variants.

Discussed in https://www.spigotmc.org/threads/spigot-api-suggestion-material-isair.397219