While there is indeed reason to go to Mass even if one cannot receive Communion, let’s deal with the more pressing concern first: That is, your friend’s apparent belief that being unable to receive Communion is a permanent status.
I do not know the situation facing your friend, but, to the best of my knowledge, there is no situation in which a Catholic presently unable to receive Communion cannot resolve the situation through the sacrament of reconciliation and the firm intention to do what is necessary to regulate his or her status in the Church. That isn’t to say that what would be required would necessarily be
easy – for example, some in irregular marriages may need to promise celibate chastity until their marriage or marital status is regulated – only that returning to a state of grace and receiving Communion is always
possible for those with the will to do so. I recommend that your friend seek out an orthodox and balanced confessor; your friend is also welcome to
contact Catholic Answers directly for more personalized assistance.
As for the initial question: The Mass is the re-presentation in time and space of the passion, death, and resurrection of Jesus Christ, something no Evangelical Protestant church can offer because such communities do not have a valid ministerial priesthood. A Catholic attending Mass does not merely hear Scripture read, sing songs, and fellowship with the congregants, as is done in Evangelical churches; a Catholic is present at Calvary and may offer up his own sufferings – such as a temporary inability to receive Communion – in union with Christ’s own suffering on the cross made present to him in time and space through the Mass.
**Recommended reading:
Mass Appeal** by Jimmy Akin
