When first learning how to bake a cake, I totally overestimated the importance of levelling a cake! Yes, it was a rookie mistake . . . which I have made MANY of. . . but any way .
Levelling a cake properly will save the cake baker tons of time whether you are just baking a cake for the family, or creating a huge 3D cake structure!
Fighting with the icing to get the levelling done properly can be avoided if you have the right tools! Does that sound like I have experience in that fight . . . why yes I do . . .LOTS! Grrr . . .