Why might a tapeworm have an expanded reproductive system compared to a planarian?

Tapeworms are hermaphroditic, like the Planaria. The difference between them is that Tapeworms can reproduce sexually, either through self-fertilization or cross-fertilization with another tapeworm, or asexually, by breaking off proglottid segments at the end of the trunk. While the 
Planaria are sexual and asexual only. Sexual planaria possess both testicles and ovaries. One of their gametes will combine with the gamete of another planarian. Each planarian transports its excretion to the other planarian, giving and receiving sperm. Eggs develop inside the body and are shed in capsules. Weeks later, the eggs hatch and grow into adults

It's cell theory. easy name i would think.