And why is it so important now for Protestants to believe that she didn't? Scripture is silent on the subject of her having other children. Surely Luther, et al were aware of the verses about the Lord's "brothers." Other than a desire to minimize Mary, is there one good reason that some Protestants insist that she had other children?
I don't think there is much argument in Christian circles about whether or not Mary was a virgin to death. There are opinions but, in truth, that is between her and Joseph.
The argument is whether we should use Mary as a round about way to get to Jesus? Do we think that if we pray to our Lord Jesus that the whole world will come to know Him tomorrow, Nov 3rd, and He won't listen to us; do we feel if we run to Mary she'll go ask her son who won't refuse her? Well why don't we pray Mary for the whole world to accept Christ tomorrow? (Oops, sorry, forgot. She won't interfere with our free will. That certainly is convenient.)
There is no reason to pray to Mary, Peter, or St. Fred. There is only one person in scripture that I know of who prayed for a dead person to intercede before God for him and it didn't go very well for him or his family.