I think this is cultural or location based – I know at least a dozen people who can weld and no one who has a 3-D printer, but I live /way/ out and rural America. The Internet would suggest that urban America is the reverse.
Sure, but if we're talking about replacing machine parts, I'm not sure how far welding will get you. You need to be able to machine custom metal parts, for parity with basic 3d printing capability.