If you want to have 1 as an output if either of two inputs are 1, why don you need an IC gate when you can just connect two wires and have one output from them?
Power.
With CMOS technology, which is pretty much everything these days, a gate drives a one by connecting the output to the +ve power rail. It drives a zero by connecting the output to ground. If you have two gates driving a single wire, one is driving high, and the other is driving low, you create a path that is connecting the power rail to ground. This will give continuous current flow and cause lots of power to be dissipated.
It also doesn't give the result you want, because the voltage on the shared output will tend to float around the centre value(*). Neither zero or one. The circuit ends up being a potential divider.
(*) assuming the size of the transistors pulling up/down is about equal.