Extrude, Revolve, Sweep, and Skin each have a property called Merge Topology. This property is a Yes/No combination box that gives you more control over feature topology. Setting the property to Yes will optimize the topology of feature bodies, while setting it to no will leave the topology of feature bodies unaltered.

The default setting for Merge Topology differs depending on the 3D feature you are using:

For example, consider a rectangular profile with a circular hole in it. Each edge is split into several pieces:

Here the profile is extruded with Merge Topology set to Yes:

Here the profile is extruded with Merge Topology set to No:

Setting the value to Yes optimizes all topology of the feature body. However, you should leave this setting as No for the Skin/Loft and Sweep features to best represent the true characteristics of the profiles. Additionally, you should be cautious when changing the value of the Merge Topology property because after initial creation, once other features depend on this, faces and edges may appear or disappear and cause failures and invalid selections for subsequent features.