No, there is no justification for bad tools. If someone makes a tool only for ASCII, fine, but don't expect that people will say it's a good tool.

Even huge sites have problems when I want to use my real name, or the name of the city I live in. They are usually made by US companies, which is strange, as you have all kinds of people there, with different names. Unfortunately the reality is that those US companies don't care about supporting normal characters people use. Even websites like Upwork don't allow me to enter my real name. Isn't that strange? I have told them about that months ago, nobody cares.

So getting to the real problem: supporting unicode is not as hard as it seems, just use from the beginning.