Do developers actually use bsp?

When blocking out a level during the early stages of development, I heard you could use bsp brushes, but do people actually use that approach?

I heard most people do the block out in external software. Is it worth just going for the meshes instantly in the engine instead of doing everything twice, or is there some big benefit I can’t really see by using bsp brushes?

You can block things out in the editor before making any of your meshes, that way people can test gameplay early and don’t have to waste any asset work if the level design changes. BSP has the advantage of being quickly edited if you want to make changes and it will automatically have collision.

You can actually convert bsp brushes into any kind of volume. I like to smother the level with bsps then convert to lightmass importance volumes. Makes it easy to see peaking out geometry that I want lit well.