Is directly working your abs even necessary?

I notice that if I keep my bf low, I get really good abs development without having to do any direct abs exercises e.g. crunches, leg raises, etc. I started to believe that doing a lot of compound lifting e.g. deads, squats, etc all work the abs, so I stopped doing any direct abs work and noticed that I maintain good definition without having to do them.  Does anyone else think that direct abs work is not really necessary as long as you keep your bf% low and work your abs indirectly with heavy lifting?
 
 

Yeah its not necessary. But isolating the abs should develop the core more than indirect work imo.