Being inactive for more than 6 months probably means you have lost interest but it does not cost any voting power, but what does cost voting power is members who join and then never post about precious metals again but use it as any other voting bot.
I used to be a fan of curation trails but it was something someone said about votes going to things they do not agree and it draining my own vp has put me off but for precious i will make a compromise and delegate 50sp anyway.
I agree with your comment. However, from a logistical sense, maintaining a list with people who seem to have dropped steemit gets unwieldy. You are correct that their continued existence as members does no benefit nor harm. It just seems inaccurate to list them as members if they are gone.
As for people who access the bot but never post about metals again... this is also a problem. But today I am tackling low hanging fruit first. ☺️
As for the vote trail, your reasoning is why I delegate.