I'd been diagnosed for 30 years without ticking the box and would have continued leaving it unticked until I found out that our insurance is null and void if we have an accident, and it's not mentioned on our licences.

The accident need not be caused by the disease, but if we or another person are injured and need to be seen by a doctor, then our insurance may be automatically cancelled because we with-held information....considered to be fraud.

It may not be the same in your country, but for me it was a no brainer, and no big deal to get the form filled out prior to each renewal. There's no way I'd ever be able to afford medical treatment, on-going or not, for any person if I was unlucky enough to be the cause of those injuries.

What I consider ironic though ... my licence actually says MS .......
"M" for medical condition, and "S" for spectacles when driving = MS.