Admission: I didn't really read the other replies; I'm just responding directly to the original poster here.
OldGuy,
Sermons aren't really a form of worship in the sense that you're used to thinking of worship in Jewish terms. Yes, it's worship, but in a different way.
Sermons have a twofold purpose beyond worship.
1) Preaching - making a point, repeatedly, by expounding upon scripture. The preacher you watched was probably using several different passages from several different books to back up his point. Us Christians NEED to be preached to - the vast majooity of us are blind to the fact that, yes, the preacher is preaching to US, and yes, we need to take him seriously. That's just the way Christians are - imperfect, but forgiven.
Preaching generallly tries to make a point about a certain pattern of behavior some Christians engage in even though they shouldn't. From a legalistic point of view, it could boil down to 'do this, dont do that'. Preaching is done because we're told to preach in the NT. Romans 10:17 says 'So then faith cometh by hearing, and hearing by the word of God'.
Also, 2 Timothy 4:2 says 'Preach the word; be instant in season, out of season; reprove, rebuke, exhort with all longsuffering and doctrine'.
2) Teaching - using scripture to expound upon a principle that will further reveal to us the nature of God, or some spiritual law that we need to understand better. Here, a lack of understanding of whatever is being taught may not be so much of a sin in a believer's life as it is a matter of just being immature or ignorant of a particular Biblical concept. Nobody ever learns everything there is to know about God, as He is revealed to us in the Bible. Teaching is a form of worship, though, as it does glorify the revealation of more of God's Holy nature.
Both preaching and teaching are useful to Christians, though I certainly agree with you that a more interactive form of worship is good. For this reason, I genuinely enjoy simple group Bible study.
Furthermore, both preaching and teaching (again, a sermon could be either or both) are useful for non-believers. We simply never know when God, through the Holy Spirit, will 'work on both ends' and make things 'click' for a non-believer.
<OK, I went and read the rest of the thread..>
As for the non-participation, many protestant churches (I can't speak for others) have 'sunday school' and often a mid-week Bible study session.
Sadly, you would be correct in assuming that for many Christians, the typical sermon is little more than entertainment. And I have heard sermons that I found to be little more than that, myself. However, there are 2 things worth remembering, as a Christian.
1) Though I *should* be able to get something out of any sermon I hear, if I'm finding it boring, I can't complain, because it may be speaking directly to the heart of someone else who is listening. It's not always about me.
2) For those charged with preaching or teaching, you can't be discouraged by those who are there merely for appearance's sake, or for mere entertainment. Scripture makes it clear that there are many false Christians, but we can't go around kicking them out of the church - if we go off stomping out the tares, as Adrian Rogers recently said, we'll often inadvertently stomp out some wheat.
Also, we're told in the Bible that some plant, some water, some harvest - you may preach to someone for years and nothing ever 'click', until they're listening to another preacher or maybe involved in some everyday event when things 'click' for them. Its humbling for me to think of the number of people who prayed for me, taught me, tried to reach out to me, tried to set an example for me, only to have things 'click' under a rather odd set of circumstances nowhere near a church building.
Anyway, that's my take on preaching. Hope this helps.