hello. This is Urban Brush designer Tammy.
If you look at the design files I have shared, most of them are design files that do not organize lines and faces.

Based on the picture of the puppy above, if you select an object, you can see that the lines and faces are alive as they are.

In addition to the shared files, I usually do not outline lines and faces like this for other works.
In most cases, it is left as is.

The reason for this, briefly, is reserved for future revisions.
In other words, based on the dog picture above, if you change the lines to planes and merge all the planes by layer,
It is quite difficult to do later work such as adding pupils or changing the shape by raising the angle of the ears.

Of course, if all lines are treated as faces and the faces are arranged,
It is good for coloring or using the finished product itself as it is.

However, if you change a line to a plane, changing a plane to a line requires more work.
If you need to change the thickness of the line, the editing process will not be smooth.

Therefore, those who ask me why the lines and planes in my work were not outlined or arranged
I hope you understand, and it has the advantage of being able to recycle and edit all files in Illustrator,
You can understand that these are the things left to use.