Mail merge for form letters? (Access is better than Excel at this too).
Yes, that's exactly what we used it for at Gigantic Soulless Pharmaceuticals, Inc.
Also, sometimes we only wanted to send something to the people in one state, or one region. I worked in Professional & State Gov't Affairs, which is where the salesmen and lobbyists were. So sometimes we wanted to send stuff to all the doctors in Kentucky, and sometimes we'd need to send something to the legislative members of Minnesota. Sometimes we wanted to send info (as for a conference) to everyone in the Southeast. For that, we needed to be able to sort and subdivide, so we had fields that never showed up in the address, like job titles and region codes. Having it in a database -- and we had thousands and thousands of records -- made it much, much easier. This is the intended use of Access and the mail merge feature in Word, and when used correctly, it's very effective.
There is no reason to use Access for any less than 100 addresses, and even then it's stupid unless you regularly send mailings to various subsets of the whole.