Plus it would be cruel for Yoshi to continuously abort his babies by throwing them against enemies.
Many animals eat their own young -- particularly in egg-laying species like fish and birds, though it's also been thoroughly documented in mammals. Shark fetuses, rather than having placentas, get their nutrition from eating each other in the womb. Not a stretch to think there's a species that weaponizes its young. There probably is one, actually; just can't think of or find one right now.
(some further reading:
[1],
[2],
[3],
[4])
A big part of the weirdness comes from yoshis being at that intersection between human and animal. Sharks and pigs and other animals that eat their young are either
djur or
varelse on
Demosthenes' Hierarchy of Foreignness; yoshis are clearly
ramen.
We live in a world with only one species, homo sapiens, firmly identified as
hnau. There's a case to be made for including other species -- cetaceans, primates, elephants, possibly even some crows and parrots -- but because we can't communicate with them (
except for when we can), we're usually mentally able to keep them securely within the animal category. But in the Mushroom World, multiple disparate species with about equal intelligence are fully able to communicate with each other and mingle freely. In examining a truly multi-species society, we're hit with heavy culture shock as we are forced to examine which of our characteristics are inherent to higher cognition, and which are specific to our primate roots -- to recognize the difference between "human" and "person."
(check out
this dude for some intriguing theorizing about multi-sapient worlds)
Going back to acting like yoshis are pretty much just human for the time being:
Also, why would Birdo be so attracted to him if he/she...whatever couldn't have sex with him?
Not all romantic relationships are sexual.
(this is using "asexual" in the human sense, referring to people who do not feel sexual desire, not the biological definition used in
Melee; it is possible that yoshis are both or neither or somewhere else entirely)
It does make sense, in a way, that the two Mario characters (for the sake of argument, treating Yoshi and Birdo as characters rather than as species) that most clearly defy human heteronormativity would share a connection.
Also... between Yoshi's tongue and Birdo's... um... "mouth"... I think they could figure something out if they wanted to take their relationship to that level.
