Can’t speak from personal experience but from what I’ve heard, it’s more about the concept / theme / emotions than the actual act itself. People (at least, the vast majority) who are into it don’t actually want to experience it in real life; just like with many other more mundane fetishes, it’s more about the fantasy and how it makes you feel to imagine yourself in that situation, and more nebulous concepts like the idea of becoming a physical part of another creature, or the imagined feeling of closeness, constriction, warmth, safety or comfort from being inside something’s stomach. Obviously not things you’d experience if it actually happened to you, but that’s not the point.