The check in/out feature is one of the core logical components of sharepoint (and not only SP, since it is a standard for other document management systems). I do not think it is advisable in the long run to dismantle such feature just because of the laziness of some users. It is obvious that they were never explained the feature and why it is there and why it should be used or not used.
I had the same problem in my current company and the strong statement of the head of the department was enough. In addition to that some 30 minutes training wouldn't hurt. As I say it is a feature that became a standard. In 2015 it is simply crazy to allow people to ignore it. It would have been like ignoring the concept of 'attachment' in the email system in the 90s.
What I have noticed in so many situations is that companies and IT departments have enough of sharepoint being up and running and the user adoption factor is completely ignored. The latter takes alone 60% of the success and return on investment of Sharepoint. Granted Wss 2.0 for you is free so it is very easy to get a ROI.
My experience is that when people are engaged they often find it fun to use (the check in/out, the versioning, doc approval) compared to boring shared drives.