Welcome to the Fermi paradox, mired in shit. Shall we itemize the errors that the tapeworm is making in its analysis?
The first and most grievous offense our tapeworm logician has committed is that of anthropocentrism (or rather, of cestodacentrism); it thinks everything revolves around tapeworms. In reality, the human is unaware of the existence of the tapeworm. This would be a good thing, from the worm’s point of view, if it had any grasp of the broader context of its existence: it ought by rights to be doing the wormy equivalent of hiding under the bed covers, gibbering in fear.
It has inferred the existence of other humans, but it doesn’t know about cooking, or the other arcane processes by which food makes its way into the gut for the tapeworm to absorb. Or about the sanitary facilities that kill tapeworm eggs before they get to another, intermediate host. There are vast, ancient, alien intellects in the macrocosm beyond the well-known human, and they are unsympathetic to tapeworms. Intrepid tapeworm cosmonauts seeking to make their way beyond the anus and across the universe to colonize other humans are in for a rough ride indeed, for they are intimately evolved to thrive in one particular environment, and that environment (the mammalian gut) is sparsely distributed throughout the universe. Much of the cosmos is inherently hostile to tapeworms. This is why tapeworms have not, in fact, colonized the universe and converted all available biomass into a constantly spawning Gordian knot of Platyhelminthic life, contra the prognostications of some teleologically-inclined tapeworm-philosophers of yore.
The human does not owe the tapeworm a living, or even a comfortable home. The tapeworm’s existence is contingent on it not damaging its human, resulting in an undesirable human/tapeworm interaction with fatal consequences for the tapeworm. Some of the tapeworm’s descendants might be able to find another new human to claim as their home, but the same constraints will apply. Only if the tapeworm transcends its tapewormanity and grows legs, lungs, and other organs that essentially turn it into something other than a tapeworm will it be able to make itself at home outside the human.