Currently there isn't an obligation to do it because there may not be any reason to be concerned. If somebody is coming in for antibiotics or you've got a very low risk patient who's on a very small amount of medication, we can't require nor would it be recommended to create barriers to appropriate treating.
This is a tool that many physicians use and it's not just related to medications. Physicians can access X-ray reports. You can actually go and look at the actual film. You can access lab data, surgical reports. It's more than just medications, but if you've got a high risk patient or a patient you're concerned about, one you don't know, you've got the ability to look a little bit further and to just minimize the risk of harm.
I think it would be a problem to obligate physicians, but it's certainly a very useful tool, and often it's a way that physicians pick up on patients that they were unaware were multi-doctoring.