I'm afraid to link to that comic since I get accused of the equivalent of rick rolling when I do.
Jeph said himself that AnthroPC libido is a mystery. Now that they have civil rights it may be illegal to take it away, but why was it there in the first place?
There was a strip where Hanners was asking her dad about a rumor she'd heard -- that true AIs hadn't been designed at all, but were the spontaneous product of a human having sex with a computer! And her father (whom we know to have created the first true AI, or at least to have been on the team that created it) awkwardly evades the question and changes the subject...
So... if it really did require sex to create the first AI, it seems likely that it will require sex to create any additional AIs. With any luck, once the first human-computer hybrids came into existence, they could reproduce by mating with each other instead of with humans.
And that's why robots have libidos!

that still doesn't explain all their other anthropic behavioral characteristics though.
for example: a human or other animal might enjoy the taste of chocolate cake mix, but only because it contains chemicals that are useful to their biological functions; it's an evolutionary adaptation to seek out glucose. pintsize however, though he has the capacity to
taste the cake mix via his hardware, has no functional reason to derive pleasure from that taste, because it's chemical composition has no relevance to the functioning of his hardware.
likewise for a lot of the other behavior we see. what in animals is an artifact of bio-chemical processes in order to fulfill a specific or general need, in non-animals appears superfluous.
i suspect one of two explanations for the behaviors we see: either emotional responses are a pre-programed app, or the AI-OS is designed to imitate/emulate behavior observed from it's social environment. in either case, why would they be built that way?
the most likely reason i can think of would be for AIs that interact with humans on a regular basis; specifically in order
to make it easier for the humans to relate to them. but then, why would it go so far as to have those simulated/emulated emotional responses override their objective/rational thinking and perception? after all, if momo loses loses her cool it's no big deal, but if
station throws a shitfit...
and that still doesn't explain the cake mix.