Is there some biblical passage where it is mentioned that in the primitive church all listened to the preacher and all were present during the whole worship?
"And they continued steadfastly in the apostles' doctrine and fellowship, in the breaking of bread, and in prayers" (Acts 2:42).
"Take heed to yourself and to the doctrine. Continue in them, for in doing this you will save both yourself and those who hear you" (I Timothy 4:16).
"Therefore we must give the more earnest heed to the things we have heard, lest we drift away" (Hebrews 2:15).
"And so we have the prophetic word confirmed, which you do well to heed as a light that shines in a dark place, until the day dawns and the morning star rises in your hearts" (I Peter 1:19).
You won't find a verse for every possible situation. Do we know that every Christian sat through the entire service and listened to every word spoken? No. But that isn't the important question. Given how important God's word is to the Christian, why won't they be wanting to learn more?
Imagine being served dinner, and a number of guests leave food on the table when it is over. Why?
- It is more than they could eat in one sitting.
- It is the same thing they have every time and they are bored with the selection.
- It wasn't properly cooked.
- It wasn't what they wanted to eat.
When it comes to the preaching of God's word, you will find similar reactions. Some preachers try to stuff more into their lesson than most can digest in one sitting. Some preachers only teach on a limited set of topics instead of teaching the whole counsel of God. Some lessons are just plain poorly organized and poorly presented. Then there are always those who are only interested in hearing what they want to hear.
When someone leaves before the end of service, it is a declaration about that person and usually not a flattering one. A feast is prepared and some just aren't that hungry.