I think for both SNK and MET (if they go down the same route) have different rationale as to why they do this.
For SNK they want to maximize the cash intake without having to do a prospectus, while it might hurt the existing shareholders in short term, but running out of liquidity in growth phase would be the last thing shareholders want anyway.
For MET, if they go the same route it would be because doing otherwise would mean little intake from the SPP, not sure how many shareholders are that keen to participate in the SPP given how this company has been performing, doubling down while you are down is hardly a good strategy to be successful in the share market.
As shown by the MRP float, I am not sure listing on ASX would change the share price much for this company.