There is evidence that early prescribing of Metformin leads to later Metformin failure (i.e. when you need to go onto other medications because Metformin alone is not enough).
There is also some evidence that Metformin has heart-protective qualities
Both might be because of the help that Metformin gives Type 2's in controlling their BG levels.
In January, my GP was talking about putting me on Met. but last month, my HbA1c level (38 mmol/mol through diet & exercise alone) led her to change her mind. Apparently, there is a faint possibility of having hypos on Met. if you are controlling BG very well by diet.