In many countries cheap/unlimited SMS was not a thing decades ago, so whatsapp filled that gap. Nowadays things got way better, but people are already used Whatsapp, and in some places companies even offer “unlimited whatsapp” in their plans, so seems unlikely to change.
Also in smaller countries whatsapp and viber were the way to communicate with friends and family in other countries. Not only messages, but audio and video calls. Audio messages are also quite important.
And groups, that’s another vector how Viber spread around, parents got to have groups with other parents from their kid’s school class.
In many countries cheap/unlimited SMS was not a thing decades ago, so whatsapp filled that gap. Nowadays things got way better, but people are already used Whatsapp, and in some places companies even offer “unlimited whatsapp” in their plans, so seems unlikely to change.
Also in smaller countries whatsapp and viber were the way to communicate with friends and family in other countries. Not only messages, but audio and video calls. Audio messages are also quite important.
And groups, that’s another vector how Viber spread around, parents got to have groups with other parents from their kid’s school class.