Interesting subject,
I think its all about expectations.
When our Troop runs into those problems (as I think all troops do form time to time) we have a little discussion at a court of honor with everyone. 1st. Scouting is a privilege, not a right. Simultaneously, in front of everyone, I tell the parents that if their son does not want to go to a scout meeting to keep him home, we dont want them at the meeting either, unless they are willing to be there. Then I tell the scouts that if they dont want to go to a meeting that they dont have to. They should tell their parents that Mr. Martin said they didnt have to go.
This is offset by a policy that says that states that we expect our High School age Scouts to make 2 meetings a month and one camp out and one outing a quarter unless they have a sports exemption. If they cannot participate at that level then they need to not be there. This also prevents a scout you havent seen in 4 years showing up 6 months before their 18th birthday and trying to pull off an Eagle Project.
The other expectation that we set is that you pay back the Troop. We dont have and older boy patrol (some troops call them green bar patrols). Our older scouts are active in their patrols and are responsible for bringing new scouts up to speed and helping to teach first year scouts the skills they need.
Many complaints of older boys are having to put up with new scouts (little kids). They are regularly reminded that they were little kids once too until some long suffering older scout showed them the ropes. Now as older scouts they need to pay back that investment of time. It also is pointed out to them that they cant very well expect the troop or the patrols to pony up time on an Eagle Project when the only thing that older scout has been doing for the last year is sitting in the corner offering sarcastic comments.
Tell them to get involved, or get out.