'Eschatology' is just everything to do with the end - whether it's personal eschatology (what happens to me in the end?) or cosmic eschatology (where is the universe headed?) - and I think we downplay it more than we should. Here are a few reasons why I think it is important that eschatology play more of a role in our teaching.
1. If we don't teach people eschatology, someone else will. I suspect that one of the reasons we don't talk about the end very much is because we don't want to be one of those loons who is always banging on about the end of the world. However, to counteract an overemphasis by largely neglecting the subject is unlikely to work! I've met several people who have been won over to dispensationalist views just because nobody else ever gave them a framework within which they could think these issues through, or a way of interpreting Revelation that seemed to take the book seriously. If we don't want people to pick up bad eschatology, we need to teach them good stuff.
2. If we don't teach eschatology, people will be disappointed with the Christian life. One corollary of our neglect of eschatology is that Christians don't understand hope, and don't understand that the best bits of the Christian life - sinlessness, seeing Jesus, freedom from suffering - are all in the future. That means that we expect more out of this life than we are really promised, and that leads to disappointment. Proper eschatology keeps us oriented to the future, with a hope and expectation that will not be disappointed.
3. If we don't teach eschatology, people don't understand how to relate to the world. What is a Christian approach to ecology? How should I think about culture? How much emphasis should we place on poverty relief and development (and which of those should be prioritised)? All of these questions need a healthy eschatology to get a good answer.
I'm sure there are more...