+1 on the "If we truly are alone in the universe, we should make our own company" answer.
In fact, we should make our own company regardless. It would better prepare us for alien modalities of thought, since uplifted organisms would have very different baseline evolutionary habits from us, and while they would be based off humans for their sapience, would still be prone to rather alien modalities of thought from us. (Not as alien as say, the hypothetical sentient amoeba from kepler 72b (made up)-- but still alien to US, and thus something to help bridge the gap and prepare us for when we may eventually meet such creature.)
However, bioethicists seem to feel that creating sentience just to create sentience is somehow immoral, and not something to do. I sometimes wonder how they reconcile their circular logic on the matter, and how they reconcile the notion of having children. (The circular logic goes like this: Creating non-human sentience, or human-animal hybrids that are sentient creates a sentient being that would not fit in with human society, and thus be ostracised-- Thus, immoral. However, when you actually think about it-- if enough of them are created, they have their own society and they dont need human society at all-- so we are basically denying them existence for our own protection, which is immoral. But creating enough of them to be their own cultural group requires first creating just a few, which means immoral point 1. Spin spin spin, rinse and repeat. Further, similar arguments were created during segregation about willfully having a mixed race child, which would not fit in with either "pure" racial cultural circle. Except that that was bullshit, as history has shown. In short, I question the actual ethics of these bioethicists.)
Now, arguments against the possible creation of new zoonotic pathogens that suddenly are now able to also infect humans, because somebody wanted a half-dolphin baby that swims in the ocean-- Those are legitimate concerns. (Endemic procine retrovirus was found to mutate very quickly in swine-human hybrid stemcell cultures, such that it could then infect pure human tissue. Something it normally cannot do. Uplifted animal people would present a massive contagion hazard to human civilization. THAT is a legitimate ethical problem. The "Wont fit in" one is bullshit circular reasoning.)