Yes, individualism is fun (and sometimes necessary), but it comes at a price.
Maybe you do provide healthy lunches, or never ever take your children out of school, and help out in whatever way you can, but there are plenty of people who don't. Schools are not in the habit of sending out personal letters to people whose behaviour is potentially upsetting the integrity of the school community, so everyone gets them, and the school hopes that the people whose children are routinely high as kites on sugar, are routinely absent or late, or are utterly unsupportive to the point of obstructiveness, might just get the message and start singing from the same hymn sheet.
The point is that a school is a community, and a community runs on rules. Rules are not flexible, nor should they be. They are there to govern the life of the community. You may question the reason behind a rule, but if you choose to ignore it rather than challenge it in an adult way (eg join the PTA or become a governor), then you are merely confusing your child, and teaching them that is OK to be an individual at the expense of the community.
Teachers and schools are not the enemy. They are the junior face of the entire community. If your child is marginalised at school, they may grow up perfectly fine, but they may also grow up lacking the ability to join their community. In my opinion, that would be doing them a disservice to encourage to regularly flout rules.
As to the suggestion that teachers owe it to pupils and parents to provide catch-up work after a term-time holiday, I can only snort and suggest that parents who find that entirely reasonable take some time to volunteer in their child's school to see first hand how much spare time teachers have...
In short, if you have a clear conscience, then you should not feel concerned by seemingly insulting letters. Yes, there really are parents who need letters written that simply.