Every mobile app has a certain language. The goal should be to offer the simplest method of achieving the end goals with a minimum learning curve. Facebook or twitter are good examples of apps that have now, through time, have been embraced as a ubiquitous part of our daily lives. Both apps have a very unique take on social media and present too very different concepts, yet the users now have become accustomed to it’s language.
Now imagine adding a new functionality to these apps that changes it’s UI. Past has proven, that whenever there is a change that is beyond the confines of user’s familiarity, there is always resistance (it’s frequency depending upon the change). The response would be similar to of betrayal.
‘Craiglist’ is a good example of an app that still looks like a relic in comparison to today’s websites, yet it has a continued patronage (steadily declining) from it’s loyal user base that became accustomed to it’s language. (whether and how the website should evolve is another question).
The above example is similar to a scenario where a rotary dial phone user, when presented with a button dial pad for the first time, is adamant to shift from what he/she is used to something that might be a better UX. And eventually will choose a rotary mechanism over a button dial pad.
Such cases beg to ask the question of whether and when to make UI/UX changes in a product and how to do make them without it becoming detrimental to the business.