Older implementations of EIGRP did not have support for wildcard masks and could only process a classful network address in the network statement (would not recognize subnet addresses). This kept EIGRP consistent with the original IGRP. Many of us learned EIGRP that way. Many examples in Cisco documentation are written that way because it is how it used to be.
Current versions of EIGRP do support wildcard masks. Use of the wildccard mask is optional (not like OSPF where the mask is mandatory) so you can configure EIGRP with wildcard mask or without wildcard mask.
Whether you need a wildcard mask (or want a wildcard mask) will depend on your situation and on what you are trying to accomplish. If all of the interfaces on the router in that network should be included in the EIGRP process (and any interface that might be added later should also be included) then configuring without a mask is easy and gets the job done. If some interface(s) on the router should be included and some interface(s) should not be included, then configuring with wildcard masks is the easy way to include what you want and exclude what you do not want. Some people like to configure with masks because it preserves the option that at some future time you might want to exclude an interface.
So it is somewhat a metter of personal preference or experience and really dependeny on the particular situation.
HTH
Rick
HTH
Rick
