A: Before we can answer this question, we must lay a foundation of knowledge which we can than pull from to arrive at a scriptural conclusion. In order to do this, we need to first broaden the scriptures that we are examining. Instead of looking at verse 9 alone, let's consider 1 Timothy 5:3-10. Starting in verse 3 the church is told to honor widows who are "really widows" (NKJV). Remember that, in New Testament times, widows didn't get government support as many do now. After the loss of their husbands, many widows would be left with next to nothing. The New Testament church saw this and attempted to minister to the widows. However, difficulties arose and they had to develop new guidelines for this particular ministry (cf. Acts 6:1-7). What we see here is part of that restructuring. The church was to distinguish between real widows, those with no one to support them, and those widows who should be entrusted to the support of family members (vss. 3-8, 16). Note that there are certain qualifications that those who are really widows have to meet and certain works required of them (vss. 5, 9, 10). With all this in mind, the answer to the question is simply because we are not told to add them to a list. We are being told in verse 9 to add them to the care of the church.