The big problem with sending supplies and fuel ahead is that there's many ways it could go wrong which would end up with the crew being dead.
There's no major advantage to sending supplies ahead of the mission to orbit another body, and a lot of risk. The thought is that you can split the cargoes and launch them in smaller, cheap rockets rather than sending up one gigantic and expensive launcher. However, you don't gain anything by sending the cargoes ahead, and if the manned spacecraft cannot rendezvous with the cargo later then the crew are dead. Rendezvous in orbit around another planet is much riskier than around the Earth as there will be much more limited and less accurate position data, and limited help from mission control due to the distance. Rather than assembling the spacecraft around Mars it makes more sense to assemble it around the Earth or the Moon and send it complete on its mission as you get the same result with the same expenditure of energy.
There's more advantage to sending fuel ahead to a Mars landing site as you can reduce the weight of the lander when it enters the atmosphere as it doesn't have return fuel. Again it's very risky as there's no possibility of aborting, and if your lander doesn't come down in the right spot the crew is also dead.
The scenario where rendezvous with a fuel tank in orbit around another body really makes sense is where the fuel was produced on the other body and sent to orbit. That capability would significantly reduce overall mission costs as there would be a lot less weight to transport, again there's the risk of a failed rendezvous, which would have to be balanced against that benefit. Plus, we don't know how to do this yet, there's been work done on producing fuel on Mars but nothing has been proven to work.
Lastly there's a time penalty. If we are sending missions to Mars we want them to focus on science, not spending half their time resupplying.