Short Messages (SMS) were very useful to send messages in real time to a mobile phone. Before smartphones becoming widely used and permanent internet connection available at reasonable prices, sending SMS was the quickest way to send brief informations without talking. Whatsapp was the first app to exploit the new digital environment to provide free SMS for everyone. Whatsapp developers had the intuition that people want things easy and were already used to SMS, so they developed something similar to SMS but sending messages as internet traffic, exactly as for emails. Nowadays the number of Whatsapp messages is reported higher that the number of SMS and many alternatives appeared, such as Telegram.
When Whatsapp was launched I wondered why people needed such a service when emails can perfectly do the job. A properly configured e-mail client can send messages in real time and received messages can pop up just like SMS. Moreover you can attach every file you want, use it on any device, also if you don't have a cell phone number.
People want it easy like SMS? Well, "it shouldn't be too hard to write an email client looking like Whatsapp" I told to myself short after Whatsapp was launched.
I just found out that I was not the one thinking about that. F-droid, my favourite software repository for Android, showed Delta Chat in the new software list. The developers not only had my same idea, but actually made it real!