This is an MMO. Even though Summoner is a traditional name for a person who calls forth a large beast the deals devastating damage in spectacular fashion, that's not viable in an MMO because of Balancing issues, making something OP, making something hard on the system when hundreds of SMNs in a FATE party call our their huge monsters and deal devastating attacks all at once.

This is not a single player game. This is an MMO. That's why SMN is a DoT job.

Hope that answers your question.