As your main reason for requesting this was:
We don't want to potentially help age discrimination from potential employers.
It's debatable that it's discrimination at all, and not simply a specific requirement for the job.
In some cases a specific age, height, 'width', etc, may be a very valid requirement, or very much desired, for a specific task, and so employers should be able to choose who they want to employ.
Just as much as work experience (can do the job), distance from the office (will likely be on time/can get in quickly in emergencies - tech support etc), is married, etc etc, can all be relevant and viable requirements for a person to be desirable for a particular position, or perhaps due to the nature of the business.
As long as the choice is relevant to the task(s) and not just discrimination based on personal views (etc).
If someone wants to employ someone younger or older than me, and wouldn't employ me specifically because I'm X years old, I wouldn't want them to waste my (and their) valuable time and financial cost allowing me to come for a pointless interview just for them to be politically correct.
I also wouldn't want to work for someone who doesn't want me to work there, so I'd rather they knew my age and singled me out from the start.