Literally people in the US choose not to get healthcare until their health deteriorates to a fatal state before going into a hospital... How can anyone defend such a stuff system?
There is a small subset of conservatives who have arguable economic/pragmatic reasons to believe that a universal healthcare system wouldn't work in the US, and then there's the other eighty percent that either instinctively reject anything that even remotely resembles a 'socialist' policy, or just a general philosophy that it's toxic to human culture to sacrifice any labor for the benefit of someone outside their immediate family. Basically, just 'forget the poor, it's my money'.
Of course the irony here is that the majority of conservatives stand to benefit from universal healthcare. The rural, working-class conservatives in Midwestern states with sky-high rates of diabetes and heart-disease would receive far more benefit to their health and finances by subscribing to a single-payer system than they would ever get from avoiding a modest marginal increase to their income tax rate. My family wouldn't personally benefit from it, but I think it's a worthwhile sacrifice.
There are even fiscal reasons to support this idea. Having a sicker populace is a burden on taxpayers. If creating a single-payer system was able to drop the incidence of certain highly-expensive preventable diseases like breast cancer and heart disease, that would translate into literally hundreds of billions of dollars of new economic productivity. You could also expect the rates of people receiving disability payments to decrease, since they would be able to receive treatment before their condition develops into something that's permanently debilitating. Likewise, people might not be receiving welfare as much when they aren't draining their entire savings account every time they have a life-threatening emergency.
Does all of that not sound like something that conservatives could get behind?
