In the beta Lanucher, the Play button on the main screen does not support some glyphs for the text written on it. It makes it aesthetically bad-looking.
The following languages are affected: Vietnamese, Tamil, Hebrew, Upside-down English, Tatar, Kazakh, Hindi. However, there's a possibility that new non-Latin languages will be added in the future and they'll require adding new characters as well.
The bug has reappeared recently, see https://bugs.mojang.com/browse/MCL-21552 for more info.