The only reason these test flights aren't reaching orbit is because they're actively aiming for a suborbital trajectory. They're not "yet to successfully launch anything from orbit", they're yet to want to go to orbit in the first place. The difference between what they get and an actual orbit is minute, relatively speaking. They've amply demonstrated that if orbit was what they wanted, they'd be there with every flight.
They're sticking with suborbital flights for now because they still have things to work on to make it more reliable, but none of them are "the rocket's too heavy"

