I can't speak to the quality of most available vet software today, but as a client, I would love to have my pets medical info in one place. Especially because I have relationships with both a local, general vet, and a specialist after my older cat got diagnosed with lymphoma. It was hard to even get those clinics on the same page at first since they were faxing ultrasounds around, and I'm still not sure if all records through. I have no way to verify. At best, I'll receive a PDF after a visit with some test results. But I don't have a comprehensive set of records online anyhwhere.
Maybe that space is already saturated or vet clinics don't have much incentive to pay for it. Still, I switched to a doctor with a better online records system (not based on the system alone though) and it definitely makes me happier with the service and less likely to switch again.