The reality is that the overwhelming number of JWs HATE the "ministry". I was just with some JW "friends" socially when they were talking about a local break spot and the direct quote (from an elder) was: "breaks are the best part of field service". While he said it as a joke, I can bet that most JWs feel the same way.
I never liked it but thought there was something wrong with me. I was out every week but once an elder, I devised a system. We lived in a rural area, so I would get a territory at least 15 minutes away, spend about half hour or 45 minutes driving from door to door, then take a break and make RVs for the rest of the morning. If it was raining, then 100% RVs.
If the WTS were to make an announcement that JWs didn't have to report their time anymore, how many JWs would still go out in service? How many would put in pioneer hours?
I think the community apathy and apathy among JWs as a whole has really diminished any zeal towards the ministry. Now, people simply go out to "get their time in".