Why would a Catholic want to attend Protestant services? Tell me please. Attending religious services is not like choosing a play to attend, a drama or a movie. Yes, it would be perfectly fine for a Catholic to attend the wedding or funeral of a good Protestant friend, sing hymns and join in prayer. Provided that the content of the prayers and songs is not contrary to the Catholic faith. But you cannot attend regular sunday services in a non-Catholic Churh. So yes Catholics can attend Protestant services, a Catholic may not, however, have a liturgical part or regularly attend non-Catholic services. Catholics may be guests at non-Catholic services - weddings, funerals, baptisms, in connection with a family gathering. But in the case of mixed spouses, the Catholic cannot consider it a level playing field, as if divine worship can be divided between the Catholic Church and the spouse’s non-Catholic Church. That would be the error of indifferentism. While the non-Catholic spouse could accompany the Catholic to Mass without limit (Communion excepted), the reverse is not true. The Catholic in a mixed marriage must respect the truth about the Church, and thus God’s will for our salvation, as well as the spouse’s conscience. That is difficult, and why the Church discourages mixed marriages to begin with.