I'm not denying it's helpful/required for accessibility, I'm just talking about 'in general' large scale use of it (or not).
Maybe it's less about glasses (if you have to find your glasses to type a message I expect you also need to in order to unlock your phone, open the app, and tap the voice message button) for older people than it is about accustom to IM - the brief chatty format is more like a telephone call than a letter.
(But those I've known to use smartphones haven't used voice messages - as distinct from telephone voicemail - anyway, as I said.)
From my anecdotal/regional experience, people over 60 prefer to use voice messages almost exclusively while younger people prefer to text.
Maybe someone at telegram or whatsapp can provide statistical data to shed more light on voice message usage.
In short, I don't think it's regional. It depends on the person with whom you need to communicate.