I'm not much for age restrictions in voting. If someone is deemed fit to serve in the military, they should be permitted to vote. I'm curious about the 75 year old age restriction too. Why? My mother exceeds that age. She's a pistol and stays tuned into politics. She has been volunteering as a poll worker since she retired. She teaches Sunday school too. The woman doesn't slow down.
Age selection may be arbitrary, but it doesn't discriminate against any particularly group--everyone has the same 40 year span to vote.
They may participate financially and be politically active. They may even hold office if those in the voting range thought they were right for the job.
At 35, most have had about 10 years of experiencing real life away from biases inherent in our educational system and, yes, our military.
If the young see a wrong, their vote would have little effect on immediate change and they would be able to vote their cause to fix what they felt was wrong when they were younger.
Similarity, at 75, their vote would probably do little to affect their remaining years.
Those in the voting range would have a chance to build an acceptable senior policy that they would soon be subject to.
In short, the voting span would reduce the inexperienced and immature voters as well as the older less-responsive-to-change and mentally deteriorating voters.
Obviously, there are exceptions for many outside that range.
For example, my brilliant perspective was lost when I was 20 (LBJ won) and my brilliance would be lost now if my suggestion was in place.
But if everyone was subject to the same rules, I would have had my fair share of voting influence.