They were, but the generation in which they were used is the pre-World War II generation, so they are dying out. These days Welsh first names are used when people want to express their 'Welshness'. But surname forms of some names survive better -
Meredith has appeared as a girls' name to run alongside the original male
Maredudd, and
Griffith for boys is fairly rare, but no rarer than
Gruffudd. And Rees/Reece may or may not be as common as
Rhys, but
Rhys is in use all over the UK now, so 'easier' spellings are common too.