Uses don't care about the code. But the language and frameworks you use have consequences for the overall quality of the user experience. The speed and responsiveness of the app, the number of bugs, turnaround time in fixing bugs, the rate at which new features are added, and the number of new bugs that occur every time a new feature is added - users care very much about those things, and those things depend on the software quality, which in turn is affected by the language and frameworks you use.