Most of these functionalities are easy to find as online apps (formatting JSON, regex validator, color picker, minifiers, etc) or can be done in REPL in one line.
Those sites could be just storing that stuff in their internal databases, breaching privacy. This app is open source, and nothing goes up to any servers.
Online apps, yur paying with yur info
devutils, yur paying with money but preserving privacy.
Convenience and saving time. I don't need these functionalities on a daily basis because I don't code on a daily basis but I totally see the point of and appeal of this app. Yes there are free online versions available for all of these things, but having them all in one place is helpful. Being from India, prices are a tad too high but not unaffordable. If I needed it, I would pay for it.