Excellent point, but I also read it as self guilt
If parents feel guilty because their children haven’t served in the military, then it’s probably because the parents have actively worked against that choice, whether for ideological or financial reasons or simply fear. If that’s where someone is, they should contribute to a private fund - help the serving troops, or Wounded Warriors, or anything that is not just giving money to the government.
We have always presented military service to our children as a highly honored option, but not the only legitimate choice. Our 21-year-old is serving (Coast Guard); our 18-year-old presently doesn’t plan on it, but the possibility is always there for him and all the others.