I agree. I'm not religious and this is all moot for me, but I can't imagine choosing to believe
because of someone else. Faith is so personal. But I can see practicing another faith (the rituals etc..) for that reason.
DH and I are different religions. I'm Hindu and he is Sikh. Neither of us are particularly religious, but we feel a cultural connection to our religion. So sometimes we celebrate holidays together, sometimes we don't celebrate then at all, and other times we do each do our own thing. My MIL is religious and she takes my son to temple with her. I don't mind that.
I get the impression that religions that have a formal conversion process are of the "you must reject all other beliefs" type. So it would be hard to convert and still hold on to your old practices.