But why doesn't the State have the right to demand that its citizens serve it in any manner except for taxes?

In any case, this isn't a matter of demanding that the citizens serve - the service is a prerequisite to voting privileges. No-one is forced to serve; but only if you serve do you get the privilege of voting.

Why is voting a birthright, as you imply? What's wrong with it being a privilege, kept for those who are willing to serve their fellow citizens?

I'm sorry, sir, but you again seem quite arbitrary, to me. Your last paragraph again appears to me quite baseless. Especially since this whole issue is about service to the state, not strictly military service.

If voting is a right of a citizen, then yes, by that definition, citizenship, in my view, should be given only to people who have served the State. Others will have to have a different status, in this case.

In some places voting is an obligation rather then a right. In Australia, for example, voting is compulsory. This applies to municipal, state and federal elections.