I Don't Understand Why You Can Only Summon in Certain Spaces, Right?

"I just feel like, specially because there's certain choices that you can make that actually make it almost easy," he says. "My tro tip for the first third of the game is find the jellyfish, ash, level it, and allow that to serve as your tank" He doesn't understand why summons are only available in specific areas or when near a bust of mariska. 'It never tells you that, as far as i know'