It's all pretty simple really.
If you are IMC at DA/MDA and the donk quits, you have virtually no choices and the safest is probably continue and hope you pop out over a runway or something flat. You are probably going to get hurt unless you are very lucky. You might make a turn if water is adjacent... but then you are going for a swim, and that is probably less appealing to most... especially in anything with a high wing (although it will probably end up on it's back, in which case you are fine).
Now extend this a bit... what about if you are IMC at DA/MDA, and it is dark? Now it's just a complete lottery.
Personally I reckon that single pilot SE IFR will only last as long as there are no serious accidents. The first big one (say a full Grand Caravan plowing into a shopping centre or a school), and I predict SE IFR will become a thing of the past (thank God).